Environ Manage (2007) 39:783–805 DOI 10.1007/s00267-005-0195-1

RESEARCH

Geyser Decline and Extinction in New Zealand—Energy Development Impacts and Implications for Environmental Management Kenneth A. Barrick

Received: 5 July 2005 / Accepted: 20 October 2006 Ó Springer Science+Business Media, LLC 2007

Abstract Geysers are rare natural phenomena that represent increasingly important recreation, economic, and scientific resources. The features of geyser basins, including hot springs, mud pots, and fumaroles, are easily damaged by human development. In New Zealand, the extinction of more than 100 geysers provides important lessons for the environmental management of the world’s remaining geyser basins. The impacts on New Zealand’s geysers are described in sequential ‘‘phases,’’ including the following: the first use of geothermal resources by the indigenous people—the Maori; early European-style tourism and spa development; streamside geyser decline caused by river level modification at the Spa geyser basin; multiple geyser basin extinctions caused by industrialscale geothermal well withdrawal at Wairakei; the drowning of geysers at Orakeikorako after the filling of a hydroelectric reservoir; and geyser decline caused by geothermal well heating systems in Rotorua City. The crisis in Rotorua prompted preservation of the few remaining geysers at Whakarewarewa—the last major geyser basin in New Zealand. The New Zealand government ordered the geothermal wells within 1.5 km of Pohutu Geyser, Whakarewarewa, to be closed, which was a locally controversial measure. The well closure program resulted in a partial recovery of the Rotorua geothermal reservoir, but no extinct geysers recovered. The implications of recent geothermal computer modeling and future planning are discussed. The New Zealand case suggests that the protection of K. A. Barrick (&) Geography Department, University of Alaska Fairbanks, Fairbanks, Alaska 99775 e-mail: [email protected]

geysers requires strong regulations that prevent incompatible development at the outset, a prescription that is especially relevant for the future management of the geothermal fields adjacent to the geyser basins of Yellowstone National Park, U.S.A. Keywords Geyser
Hot spring
Fumarole
New Zealand
Geothermal energy
Yellowstone National Park

Introduction Landscapes that contain geysers, hot springs, mud pots, fumaroles, and other hydrothermal features are important natural resources that provide recreation, economic, scientific, and education benefits. Millions of tourists, and a dedicated community of advocates—often referred to as ‘‘geyser gazers’’—have patiently waited to capture the awe-inspiring spectacle of a geyser in full eruption, discover the mystery of nearby caldrons of hot water and steam, and enjoy adjacent multicolored mineral terraces. In addition, hydrothermal landscapes provide important economic benefits that extend well beyond those obtained from recreation and tourism. The water from hot springs can be diverted to spa bathing facilities in order to market the therapeutic qualities ascribed to mineral waters. Geyser basins also provide valuable scientific and education assets. Beyond their geologic importance, a host of rare and interesting flora and fauna inhabit geyser basins. A flurry of recent scientific inquiry is focused on the special properties of thermophilic organisms, including Eubacteria, Archaea, and Eucarya. These organisms are adapted for survival in

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extremely hot water, thus making them important catalysts in industrial processes. For example, an enzyme isolated from the bacteria Thermus aquaticus, which was discovered in a hot spring in Yellowstone National Park, U.S.A., is the driving ingredient in the polymerase chain reaction that made DNA testing possible. In effect, a single species of bacteria, once dwelling only in hot springs, now supports the essential DNA replication industry that generates many billions of dollars (Milstein 1995). A virtual ‘‘stampede’’ of biological prospecting is now under way in hot springs to discover unknown but potentially valuable species. There is yet another emerging service of geyser basins. They are increasingly viewed as part of what constitutes the host country’s national identity—that which contributes to a sense of place. Today, there are only a few geyser basins in the world—in Yellowstone National Park, northwest Wyoming, U.S.A. (about 300 geysers); Dolina Geizerov, ‘‘Valley of Geysers,’’ on the Kamchatka Peninsula, southeast Russia (about 200 geysers); the El Tatio Geyser Field in northern Chile (about 80 geysers); Iceland (about 18, not all active); the North Island of New Zealand (about 30 remaining); and some other places with single (or a few) geysers (Houghton and others 1980; Rinehart 1980; Glennon and Pfaff 2003). The scarcity of geysers is exacerbated by the relative ease by which human endeavors can irreversibly extinguish them. Geothermal water can also be used for the production of electricity, for residential and commercial heating, and/or to supply spa pools. Geothermal energy production often requires wells that extract large amounts of hot water, steam, and/or heat from the geothermal reservoir. Artificial withdrawal is capable of quenching natural overflow features like geysers. When geothermal wells lower reservoir pressure, the discharge can be reduced to the point where geysers cease to play (Houghton and others 1980). After artificial quenching from well withdrawal, geysers almost never recover. Although the exact mechanism is unknown, it is suspected that underground cooling results in the geyser’s plumbing becoming clogged with mineral precipitates, rendering it extinct. Therefore, geyser quenching from geothermal well withdrawal must be viewed as an irreversible commitment. The global search for energy is likely to increase demand for geothermal energy. In 2001, 21 nations were generating electric power with geothermal energy, and during the last half of the 1990s installed capacity increased more than 15% (Huttrer 2001). New technologies are likely to push development into geothermal fields that were once marginal. New

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designs include much smaller (5 MW) geothermal power-generating units, which are lower cost, require less installation time, and allow the staged development of geothermal reservoirs (Freeston 1991). Therefore, where geysers and hot springs are to be protected, environmental managers must understand the potential negative impacts of geothermal energy development on these features. Because impacts can radiate many kilometers from geothermal well fields, important geyser preserves are vulnerable, like those in Yellowstone National Park. For example, the ‘‘Island Park Known Geothermal Resource Area,’’ located near the southwest corner of Yellowstone, is not far from the world’s most important concentration of geysers at the Upper Geyser Basin, including Old Faithful Geyser. The Island Park geothermal field is managed by the U.S. Forest Service under a multiple-use classification, and has been studied for future geothermal development (U.S. Forest Service 1980). Moreover, geothermal wells have been drilled near the northern border of Yellowstone, not far from Mammoth Hot Springs. Also, the ‘‘Corwin Springs Known Geothermal Resource Area,’’ located north of Yellowstone is vulnerable to the potential for nearby geothermal development. The geyser basins in other parts of the world are also potentially vulnerable. New Zealand once had the second largest array of active geysers in the world (second only to Yellowstone). However, energy projects reduced New Zealand’s predevelopment endowment of more than 130 geysers (Houghton and others 1980) to about 30 remaining important geysers. Among New Zealand’s 5 major geyser basins, 4 were extinguished or negatively impacted by energy development (Wairakei, the Spa, Orakeikorako, and Whakarewarewa), and one basin was greatly modified by a volcanic eruption (Rotomahana). The geysers at Wairakei Geyser Valley and the Spa geyser basin were extinguished by the production wells of the Wairakei Geothermal Power Station, while the number of geysers at Orakeikorako were greatly reduced when the hydrothermal field was partially flooded by the Ohakuri hydroelectric reservoir. The geysers at Whakarewarewa, part of the last major geyser concentration in New Zealand, were negatively impacted by geothermal wells supplying home and commercial heating systems in Rotorua City. The protection of Whakarewarewa’s few remaining geysers required controversial government regulations that forced the closure of many geothermal wells. The preservation of the world’s remaining geyser basins will benefit from a clear understanding of

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Fig. 1 The Taupo Volcanic Zone and associated geothermal fields on the North Island of New Zealand (after Waikato Regional Council 1991)

New Zealand’s geothermal resource development. I analyze 14 ‘‘phases’’ that document the multiple causes for geyser decline, the sequence of events leading to geyser extinction, and the environmental management implications. As a whole, these phases describe a classic environmental saga with an evolving array of hydrothermal resource uses and emerging values. The early phases of development introduced the consumptive use of geyser basins, then concern for the conservation of surface hydrothermal features emerged, and when it was nearly too late, steps were taken to preserve the few remaining geysers.

Taupo Volcanic Zone and the Classification of Hydrothermal Features The main geothermal fields in New Zealand are located on the North Island in the Taupo Volcanic Zone (Fig. 1). Technically, the Taupo Volcanic Zone is a complex volcano-tectonic depression largely filled by felsic lavas and pyroclastics (Simmons and Browne

1991). The volcanism is the result of lithospheric plate movement—the Pacific Plate is subducting beneath the Indian–Australian Plate. The Taupo Volcanic Zone marks the onshore termination of the Tonga-Kermadec Tectonic Arc (Simmons and Browne 1991). It is about 250 km long and some 60 km wide, extending in the north from the White Island volcano in the Bay of Plenty to the andesitic volcanoes of Tongariro, Ngauruhoe, and Ruapehu in the south. Geysers and other hydrothermal features are all manifestations of large underground plumes of geothermal heat, which move to the surface on convection currents that develop in groundwater. By definition, a geyser is a hot spring that intermittently becomes unstable and ‘‘erupts’’ (usually upwards) a turbulent mixture of water and steam (and/or gas, like CO2), which is sometimes followed by a vapor phase (White 1967). Eruptions, and the intervening quiescent recharge phase, are cyclic so that geyser activity is approximately periodic, and sometimes predictable. Geysers can be classified according to the type or shape of the eruption (Rinehart 1980).

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Surface hydrothermal features are classified into 2 groups: (1) geysers and hot springs, and (2) acidsulfate pools, fumaroles, and mud pots. Geysers and hot springs represent the emergence of deep reservoir fluid. They typically discharge clear water at near boiling temperature, with chloride usually the dominant anion (Houghton and others 1980; Simmons and Browne 1991). The second group comprises acid-sulfate pools, including fumaroles and mud pots. A fumarole is a vent that discharges steam and other gases, but not liquid water (White 1968). Acid-sulfate features result from steam heating of shallow groundwater (as opposed to deep reservoir fluid). They have little or no water discharge (Lloyd 1975), and contain suspended mud generated by the dissolution of volcanic rock (Simmons and Browne 1991). Geysers are rather ephemeral features, especially when viewed over geologic time. They are also rather improbable, given their delicate underground plumbing and the upheavals that are common on the volcanic landscapes that favor their formation. In New Zealand, the Waimangu Geyser was an excellent example of a short-lived geyser. It was created after the eruption of the Mt. Tarawera volcano in 1886, which opened large vents near Lake Rotomahana. Lake Rotomahana is located about 250 km southeast of Auckland (Fig. 1). Waimangu, a Maori name meaning ‘‘black water,’’ was the world’s largest geyser, with unusually tall and violent eruptions, sending huge volumes of hot water and mud from 100 to 500 m into the air. However, the life cycle of Waimangu was limited to eruptions between 1900 and 1904. Currently, all that remains is a mostly infilled crater. Waimangu was a testament to the geologically ephemeral nature of geysers, which contributes to their scarcity value.

Phases of New Zealand’s Hydrothermal Resource Development The events that led to the permanent loss of more than 100 of New Zealand’s geysers are best described in 14 ‘‘phases.’’ The phases describe the sequential impacts of New Zealand’s energy development on geyser basins. Some of the phases overlap in time somewhat because of simultaneous projects. As an aid to keeping track of major events, Fig. 2 provides a timeline summary. A list of selected geysers, and where applicable, their cause of extinction are provided in Table 1. Photographs of selected geysers that were driven to extinction by energy development are pro-

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vided in Fig. 3 in order to illustrate the loss to New Zealand’s environmental legacy. These geysers will never play again. The early development decisions taken by the New Zealand government (hereafter referred to as ‘‘Government’’) were made without advance knowledge about the potential impacts on geysers. Currently, environmental managers can predict the irreversible loss of geysers when development competes for geothermal water and/or heat, and much of that knowledge comes from the lessons learned from the New Zealand experience.

Phase 1. First Use—the Maori The Maori are New Zealand’s aboriginal people, and they were the first users of geothermal heat in New Zealand. The Maori currently represent about 10% of the population. The Maori used geyser basins in many ways, including as sacred ritual space, for therapeutic and medicinal uses, and as a source of warmth for heating, cooking, drying berries, bathing, laundry, and the dyeing of fibers (Houghton and others 1980). Several tribes, including Te Arawa and Ngati Tuwharetoa, located their settlements around hot springs. Although the Maori used some hot springs for generations, their traditional uses did little to modify the natural features (Houghton and others 1980). Therefore, the Maori traditional use phase was essentially nonconsumptive. Based on their long history of use, and the sense of place that continuous occupation fosters, the Maori continue to place a high value on geysers and hot springs. The Maori consider themselves the kaitiaki (guardians) of the geothermal taonga (treasure) and actively support holding geothermal assets in trust for future generations (Tutua-Nathan 1988). Today, New Zealand’s ‘‘Resource Management Act’’ 1991 provides the Maori with specific rights for participation in the environmental management of geothermal resources.

Phase 2. Early European Spa Development and Tourism New Zealand’s geyser basins became important tourist destinations soon after European settlement. From the mid-1800s, tourists could look at geysers and hot springs, and sit in mineral pools. In addition, the curative and ameliorating properties ascribed to mineral baths were at the height of fashion. The therapeutic value of mineral waters spawned the term ‘‘the

1890

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1965

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1975

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1995

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Geothermal tourism begins at Wairakei Geyser Valley Geothermal exploration for electricity production begins Geothermal test well withdrawal begins At Geyser Valley, hot spring water level decreases At Geyser Valley, Great Wairakei Geyser stops playing Numerous hydrothermal eruptions begin at Karapiti Electricity production begins at Wairakei Geothermal Power Plant Ground subsidence begins at geothermal well field At Geyser Valley, all 22 geysers extinct

Waikato River hydroelectric control gate installation at Lake Taupo outlet Waikato River deepened, all geysers stop erupting Wairakei geothermal wells (5 km distant) cause geyser extinction

New production wells maintain geothermal pressure Reinjection wells installed

Some 750 (75% of total) hot springs and geysers drowned by filling Ohakuri hydroelectric reservoir

Fig. 2 Time-line summary of geyser and hot spring decline and extinction in New Zealand

Wairakei

Spa, Taupo

Orakeikorako

Spa and bathhouse based geothermal tourism develops Whakawarewara thermal area declared a scenic reserve First shallow geothermal wells drilled for home and commercial heating Rachael Spring and Malfroy Geysers fail Geothermal well development increases rapidly Geothermal Energy Act requires license for geothermal wells Slight decline in surface hydrothermal features noticed Government transfers geothermal management to Rotorua Whakarewarewa hot spring decline becomes widely recognized Geyser conservation movement begins New wells banned within 1.5 km of Pohutu Geyser Geothermal reservoir declines up to 5 m, 2 m at Whakawarewera Papakura Geyser fails, Parekohoru and Korotiotio hot springs fail Pohutu Geyser eruptions are short Only 38 of 63 features at Whakarewarewa still boiling Only 4 of 16 geysers at Whakarewarewa still erupting Pohutu Geyser exhibiting low energy eruptions Urgent need to save remaining geysers at Whakarewarewa Government revokes local geothermal management Geothermal well “closure” ordered within 1.5 km of Pohutu Geyser Well license, royalty, and conservation measures imposed in Rotorua Public protest of geothermal well closure program Pohutu Geyser resumes longer and higher eruptions Parekohoru spring resumes outflow, but Korotiotio does not recover 376 geothermal wells reduced to 140 Partial geothermal reservoir recovery, level increases 1-2 m Some Whakarewarewa features show increased activity Geothermal well reinjection required Well withdrawal increases modeled No extinct geysers recover

Rotorua City and Whakarewarewa

Mid-1800’s—geyser and hot spring based geothermal tourism develops Mt. Tarawera volcano erupts destroying the terraces and nearby tourism facilities

Pink and White Terraces

1880

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Table 1 Fate of selected geysers in New Zealand—current status, probable cause of extinction and eruption height Geyser Basin (area) Geyser name

Status

Probable cause of extinction

Eruption height in m

Source

Ohinemutu (Lake Rotorua) Great Waikite

Extinct

Natural

14

Meade 1870

Orakeikorako Albert Bird’s Nest Cascade Cauldron Coral Diamond

Flooded Flooded Activea Flooded Flooded Dormant

Reservoir filling Reservoir filling — Natural Reservoir filling Natural

3 2.4 na 4.6 15 3–9

Dreadnought Erupting Cauldron (Ngahapu) Hochstetter Jewel Kurapai Mimi Homai-o-te Rangi Minginui Ngahapu Ohaki Orakeikorako Porangi Prince of Wales Feather

Dormant Flooded Dormantb Flooded Active Flooded Flooded Na Flooded Flooded Flooded Dormant

— Reservoir Natural Natural — Reservoir Reservoir na Reservoir Reservoir Reservoir Natural

na 4.6 2.4 1.8 6 24 4.5 na 15 63 24 3

Psyche’s Bath (Rock and Roll) Pudding Basin Rahu Rahu Rameka Ruakiwi Sea Egg

Dormant Flooded Flooded Flooded Flooded Flooded

Natural Reservoir Reservoir Reservoir Reservoir Reservoir

filling filling filling filling filling

18 9 40 6 1.3 0.5

Split Te Mimi-a-Homaiterangi Te Wahine

Flooded Flooded Dormant

Reservoir filling Reservoir filling Natural

3 10 1.8

Terata Twin Geysers Wainui Waipapa

Flooded Flooded Flooded Flooded

Reservoir filling Natural Reservoir filling Reservoir filling

25 na 10 2

Lloyd 1972 Lloyd 1972 Lloyd 1972 Lloyd 1972 Lloyd 1972 Edwards F. Lloyd, New Zealand Geological Survey, 2006, personal communication Lloyd 1972 Lloyd 1972 Lloyd 1972 Lloyd 1972 Lloyd 1972; Koenig 1992 Lloyd 1972 Lloyd 1972 Lloyd 1972 Lloyd 1972 Lloyd 1972 Lloyd 1972 Edwards F. Lloyd, New Zealand Geological Survey, 2006, personal communication Lloyd 1972 Lloyd 1972 Lloyd 1972 Lloyd 1972 Lloyd 1972 Edwards F. Lloyd, New Zealand Geological Survey, 2006, personal communication Lloyd 1972 Hochstetter 1864; Lloyd 1972 Edwards F. Lloyd, New Zealand Geological Survey, 2006, personal communication Lloyd 1972 Lloyd 1972 Benseman 1965 Lloyd 1972

Extinct Extinct Extinct Extinct Extinct Extinct Extinct Extinct Extinct Extinct

Geothermal Geothermal Geothermal Geothermal Geothermal Geothermal Geothermal Geothermal Geothermal Geothermal

30 — — — — — 3 — 6 30

Thompson Thompson Thompson Thompson Thompson Thompson Thompson Thompson Thompson Thompson

Spa, Taupo Crow’s Nest Eileen Ethel Eunice Hazel Paddle Wheel Paddle Wheel Ben Unnamed (near Crows Nest) Unnamed (near Paddle Wheel) Waipikirangi

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filling

filling filling filling filling filling

wellsc wellsc wellsc wellsc wellsc wellsc wellsc wellsc wellsc wellsc

1957 1957 1957 1957 1957 1957 1957 1957 1957 1957

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Table 1 Continued Geyser Basin (area) Probable cause of extinction

Eruption height in m

Natural Natural

12 6

Hochstetter 1864 Grange 1937; Edwards F. Lloyd, New Zealand Geological Survey, 2006, personal communication

Waimangu-Rotomahana Pink and White Terraces Te Tarata Extinct Natural Waimangu Extinct Natural

20 460

Mair 1876 Simmons and Browne 1991

Waiotapu (23 km SSE of Rotorua) Lady Knox (engineered ) Active

—

20

Ronald F. Keam, University of Auckland, 2006, personal communication

Wairakei (Geyser Valley) Black Bridal Veil Donkey-Engine Dragon’s Mouth Eagle’s Nest Prince of Wales Feather Funnel Great Wairakei Haematite Heron’s Nest Little Wairakei Packhorse Paddle Wheel Satan’s Eye Twins Te Rekereke

Geothermal Geothermal Geothermal Geothermal Geothermal Geothermal Geothermal Geothermal Geothermal Geothermal Geothermal Geothermal Geothermal Geothermal Geothermal Geothermal

1 na na na na na na 21 na na na na na na 5 na

Grange 1937; Stokes 1991 Thompson 1957 Stokes 1991 Stokes 1991 Stokes 1991 Stokes 1991 Stokes 1991 Grange 1937; Stokes 1991 Glover 1977 Stokes 1991 Stokes 1991 Stokes 1991 Grange 1937 Stokes 1991 Grange 1937; Stokes 1991 Stokes 1991

3 1–10 5–7 5–10 4 na 4 6 15–30 2–12 na 1–10 20 6 na na 60 30

Ministry of Energy 1985 Ministry of Energy 1985 Lloyd 1975 Malfroy 1891 Gordon 2005 Cody and Scott 2005 Gresham and others 1983 Lloyd 1975 Ministry of Energy 1985 Ministry of Energy 1985 Lloyd 1975 Ministry of Energy 1985 Wohlmann 1907 Ministry of Energy 1985 Lloyd 1975 Lloyd 1975 Ministry of Energy 1985 Lloyd 1975

Geyser name

Status

Tokaanu (Lake Taupo-Southern Shore) Pirori Extinct Taumatapuhipuhi Rare

Extinct Extinct Extinct Extinct Extinct Extinct Extinct Extinct Extinct Extinct Extinct Extinct Extinct Extinct Extinct Extinct

Whakarewarewa and Rotorua Houriri Extinct Kereru Rare Mahanga (Boxing Glove) Dormant Malfroy Geysers Extinct Okianga Dormancies Ororea Extinct Papakura Extinct Pareia Occasional Pohutu Active Prince of Wales Feather Active Puarenga Extinct Te Horu Extinct Waikite Extinct Waikorohihi Active Waiparu Extinct Waiporu Extinct Wairoa Extinct Whakamanu Extinct

wells wells wells wells wells wells wells wells wells wells wells wells wells wells wells wells

Natural — — Spa withdrawal Natural Geothermal wells Geothermal wells — — — Natural Geothermal wells Geothermal wells — Natural Natural Geothermal wells Natural

Source

a

Eruptions commenced in 2006 after dormancy of about 40 years (Edwards F. Lloyd, New Zealand Geological Survey, 2006, personal communication) b Geysering action began after reservoir filling, continued for several years, but returned to pre-filling status (Edwards F. Lloyd, New Zealand Geological Survey, 2006, personal communication) c Geyser decline from river water level modification, then extinguished by geothermal wells na = information not available

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Fig. 3 Selected New Zealand geysers that are now extinct because of energy development. A Crow’s Nest Geyser, the Spa geyser basin (Lloyd photo); B Waipikirangi Geyser, the Spa (Lloyd photo); C Prince of Wales Feather Geyser, Geyser Valley (Isles photo); D Twins Geyser, Geyser Valley (photographer unknown); E Porangi Geyser, Orakeikorako (Lloyd photo); and F Waikite Geyser, Whakarewarewa (Lloyd photo)

taking of the waters,’’ and provided impetus for the development of the North Island’s spa-bathing facilities (BPRC 1994). The Pink and White Terraces became one of New Zealand’s first popular tourist destinations. The terraces were located on the shore of Lake Rotomahana (Fig. 1), and were world-class landscape features—complete with an erupting geyser, hot springs, and colorful deposits. Silica sinter formations stepped down about 25 m to the picturesque lakeshore (Simmons and Browne 1991). Two prominent hot springs, Otukapuarangi and Te Terata (also the geyser), fed the terraces. Tourism was based primarily on viewing the terraces—hot spring bathing was

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subordinate, because the natural pools were the only bathing facilities. Unfortunately, the magnificent terraces came to a catastrophic end. On June 10, 1886, the nearby Mt. Tarawera volcano erupted and obliterated the terraces, greatly modified the nearby hydrothermal features, and destroyed the tourism facilities. After the volcanic destruction of the Pink and White Terraces, the focus of geothermal tourism shifted to Rotorua City, located about 190 km southeast of Auckland (Fig. 1). Bathhouse and spa construction began in the early 1880s. Shortly thereafter, an advisory medical position was created (Rockel 1986). In Rotorua, the popularity of ‘‘taking of the waters’’

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and the hospitality of the local Maori resulted in impressive spa growth. In 1891, there were an estimated 10,000 spa baths/year, and by 1904, the number of spa baths grew to 100,000/year (Ministry of Energy 1986). In 1908, the famous Rotorua Bathhouse was constructed (then called ‘‘The Great South Seas Spa’’). The Bathhouse was designed in a neo-Tudor style, and the basement contained a mud bath complete with specialized balneological equipment. The Bathhouse was located in the ‘‘Government Gardens (or Sanatorium Grounds),’’ which was designed and manicured in the style of an Edwardian Garden. Camille Malfroy, a district engineer from 1886 until 1896, constructed the Gardens, including 3 main hot springs: (1) Rachel Pool, (2) the Malfroy Geysers, and (3) the New Priest Spring (Houghton 1982). The main engineered feature, Malfroy Geysers, had concrete tubes installed in the vent of a hot spring (Houghton 1982), and managers could mechanically control the eruption cycle (Wohlmann 1907). The Malfroy Geysers became an important early tourist attraction. Currently, the Rotorua Bathhouse is no longer a spa, but is operated as the ‘‘Rotorua Museum of Art and History.’’ Spa bathing has long been perceived by its adherents as providing various therapeutic benefits. Spa bathing was thought to be useful for ameliorating rheumatic conditions, asthmatic conditions, and skin afflictions (Wohlmann 1907). Many early spas had specialized balneological equipment to induce or enhance the desired effects, including electrical treatments. The

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public’s faith in spa treatments began to decline somewhat in the 1920s. Nonetheless, the belief in the restorative powers of the ‘‘taking of the waters’’ has never died out, and no doubt underpins the recreational value of spa bathing today. In particular, many residents of Rotorua remain committed to the hydrothermal lifestyle, and many believe in the curative power of hot mineral water. The geysers and hot springs of Whakarewarewa, conveniently located at the southern margin of Rotorua City (Fig. 1), provided another enduring tourism asset (Lloyd 1975). Whakarewarewa was declared a scenic reserve in 1898, and represents a world-class tourism destination providing excellent examples of geysers, more than 500 hot springs, fumaroles, sinter deposits, and geyser eggs. Today, Whakarewarewa’s Geyser Flat has 7 geysers, including Waikorohihi, Pohutu (major attraction), Prince of Wales Feather, and Te Horu (Lloyd 1975). A map showing the location of these geysers, and other important hydrothermal features, is provided in Figure 4. Five of these geysers erupt frequently, and they represent New Zealand’s last remaining concentration of active geysers (Houghton and others 1980). Whakarewarewa is part of what makes New Zealand ‘‘different,’’ and greatly contributes to a sense of national pride. Recent estimates of the economic value of Rotorua’s geothermal tourism suggests it contributes about NZ$310 million/year, and tourism is directly or indirectly responsible for 18% of all local employment (Butcher and others 2000).

Fig. 4 Selected geysers and hydrothermal features at Whakarewarewa, located on the south edge of Rotorua City (after Houghton 1982)

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Phase 3. River Changes and Geyser Dormancy at the Spa Geyser Basin Geyser basins are often located on the banks of rivers where groundwater emerges as springs. Therefore, any permanent change in the discharge or water level of the river can greatly impact streamside geysers or hot springs. The fate of geysers at the Spa geyser basin, located near Taupo, provides an excellent example. The hydrothermal features at the Spa were situated along the banks of the Waikato River about 2 km below the outlet of Lake Taupo. Lake Taupo is about 60 km south of Rotorua (Fig. 1). The Spa had several geysers that were important tourist attractions, complete with hot springs, mud pools, and steaming ground. It was common at the Spa for a natural drop in river level to be associated with a decrease in chloride spring discharge (probably caused by changes in ground-water level). In extreme cases, the spring flow ceased altogether, with the water receding about a meter down the vent of the spring (Thompson 1957). In the late 1930s, control gates were built across the Waikato River just below the outlet of Lake Taupo. The gates were built to convert the lake into a storage reservoir for downstream hydroelectric generating stations. To facilitate the free flow of water from the gate, the downstream river channel was permanently deepened at the Spa. Following the river lowering, the Spa geysers stopped erupting, including the famous Crow’s Nest Geyser (Fig. 3) and Waipikirangi Geyser (Fig. 3) (Thompson 1957). There was an attempt to rejuvenate Crow’s Nest Geyser by lowering its overflow vent to match the lowered river level. The engineering fix worked—Crow’s Nest Geyser resumed intermittent eruptions. However, a few years later, the pressure drop induced by the geothermal wells at the Wairakei Geothermal Power Station (discussed later) caused the boiling chloride water to disappear from the Spa hot spring vents and all the Spa geysers became extinct (Houghton and others 1980). In summary, the initial decline of the Spa geysers suggests that any development activity that permanently lowers the nearby river water level is capable of causing the dormancy or extinction of streamside geysers. The river channel modification at the Spa was the first recorded evidence of human caused disruption of geysers in New Zealand.

Phase 4. Industrial Scale Well Development for Geothermal Energy Electricity production in New Zealand was becoming inadequate to meet increasing demand by the late

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1940s, a condition that was exacerbated when local drought limited hydroelectric generation (hydro accounted for about 80% of total production). The Government’s search for energy alternatives included the geothermal potential of the Taupo Volcanic Zone. The geothermal resource was estimated to be equivalent to about 2000 MW of electricity, which was half of New Zealand’s total generating capacity at the time (Bolton and Studt 1977; Donaldson and Grant 1978; Lumb 1980). The Government ascribed several benefits to geothermal power production, including (1) the diversification of the country’s energy options, (2) dependable base-load power production, and (3) international leadership in the development of geothermal technology, which spurred the creation of the ‘‘Geothermal Institute’’ at the University of Auckland (Fry 1985). By 1995, the actual installed capacity of geothermal generating stations was 440 MW, which accounts for about 5% of New Zealand’s electricity-generating capacity (Huttrer 2001). A feasibility study was undertaken to determine whether geothermal power could be produced at the Wairakei Geothermal Field (Birsic 1974), which is located about 55 km south of Rotorua City, or just a few kilometers north of Lake Taupo (Fig. 1). The Wairakei area had geysers, hot springs, and fumaroles acting like a divining rod pointing the way to a developable geothermal resource (Fry 1985). Test drilling began in 1950. Two years later, the ‘‘Geothermal Steam Act’’ of 1952 granted the Government authority to develop geothermal power. In 1953, the ‘‘Geothermal Energy Act’’ was passed, which gave the Government the sole right to take and use geothermal energy (Stokes 1991). Then, Wairakei’s first deep well (about 600 m) was drilled (Simmons and Browne 1991). Electricity production began in 1958 (Birsic 1974). The Wairakei Geothermal Power Station is a base-load facility, which continuously generates at full power (Axtmann 1975). Wairakei’s current generation is about 165 MW (1 MW can provide enough power for about 1000 people) (Allis 1981; Huttrer 2001). About 100 geothermal wells have been drilled to supply the Wairakei power station (Fig. 5). Wairakei was only the second geothermal power station to be built in the world, and the first to use a liquid-dominated system (as opposed to steam). A second geothermal power station was investigated at the Ohaaki-Broadlands Geothermal Field, which is located along the Waikato River, about 23 km northeast of Wairakei (Fig. 1). Deep chloride water upwells on both sides of the river at Ohaaki-Broadlands (Simmons and Browne 1991). An engineering investigation was conducted from 1966 to 1971, and 25 wells

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Fig. 5 Wairakei geothermal well field and power station, including the location of Geyser Valley, Karapiti, and Waiora Valley ca. 1960 (after Allis 1981)

were drilled with a proven output of 120 MW. In 1989, the Ohaaki Geothermal Power Station began electricity production. However, the geothermal field has declined, thus causing the high-pressure steam production at the power station to decrease to about 50 MW. Three new wells were drilled in 1995, and some existing wells were deepened in order to increase the power station’s useful life (Huttrer 2001).

Phase 5. Wairakei’s Well Withdrawal and Crisis at Geyser Valley Wairakei Geyser Valley was one of New Zealand’s major hydrothermal attractions (Grange 1937; Glover 1977). Geyser Valley was located on the northeast margin of the Wairakei Geothermal Field (Fig. 5). The location of selected Geyser Valley geysers and other important hydrothermal features is shown on Figure 6. Local spa bathers, tourists, and the Maori valued the therapeutic qualities of the hot springs. The allure of Wairakei’s hydropathic treatments prompted Robert Graham to develop a spa at the nearby Geyser House Hotel (Stokes 1991). By the 1890s, the Geyser House Hotel had developed into a tourist hotel. Hot pools

were the major attraction, but it was also a point of departure for touring Geyser Valley (Stokes 1991). There were a total of 244 thermal features in Geyser Valley (Gregg and Laing 1951), including 22 geysers, and 122 features that displayed cyclical flow characteristics (Waikato Regional Council 1991). The geysers at Geyser Valley erupted on frequent, more predictable cycles than those at Whakarewarewa (Wohlmann 1907). A major geyser was the Great Wairakei Geyser, which erupted infrequently to a height of about 30 m. Other interesting geysers included the Bridal Veil, Dragon’s Mouth, Eagle’s Nest, Prince of Wales Feather (Fig. 3), and the Twins (Fig. 3). In addition, there were mud pots, boiling springs, multicolored silica terraces, and lakelets. The valley, like other hydrothermal areas in New Zealand, was habitat for an assemblage of interesting thermally adapted vegetation, including mosses, lichens and rare ferns. The Waiora Valley (now called Bore Valley) contained another cluster of colorful hot springs, and was considered to be one of the choicest hydrothermal assets in the Wairakei area (Stokes 1991). Waiora Valley is located about 1.5 km southwest of Geyser Valley (Fig. 5). Waiora’s more famous features included Blue Lake (Pirorirori), Red Lake, and Mud Frog Pond.

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Fig. 6 Geyser Valley and location of selected geysers and hot springs before geothermal well production at Wairakei, ca. 1950. All geysers now extinct. (after Stokes 1991)

Karapiti (now called Craters of the Moon) was another distinctive hydrothermal area, which featured a large fumarole (also called Karapiti or blow-hole). Karapiti was located about 3 km southwest of Geyser Valley (Fig. 5). The fumarole at Karapiti was large enough for its steam column to be seen from afar, and was famous because of the deafening roar generated by a constant and powerful jet of steam flowing through a narrow vent (Stokes 1991). When electricity production began at Wairakei, the massive well withdrawal resulted in changes in the depth of the reservoir’s steam–liquid interface. The pressure decline induced boiling and produced vapordominated zones in areas that were formerly liquiddominated (Simmons and Browne 1991). In the western part of the reservoir, the overall drop in the water level was about 300 m. Geothermal fluid withdrawal has also resulted in ground subsidence. Total subsidence now exceeds 10 m, which is a world record for subsidence due to fluid withdrawal, including oil, gas, groundwater, and geothermal (Simmons and Browne 1991). The first changes were recorded in Geyser Valley as early as 1952, shortly after geothermal well withdrawal began at Wairakei (Thompson 1957). Selected Geyser Valley hot springs were monitored in 1953 and 1954, and a decrease in water discharge was observed, with a trend toward more alkaline conditions, including changes in chloride content (Grange 1955). The decrease in hot spring discharge was especially pronounced at higher elevations (Thompson 1957).

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Also, there were irregularities in geyser activity. It was noticed that some of the Great Wairakei Geyser’s eruptions were much shorter (McCree 1957). Moreover, between 1952 and 1954, the average period between the eruptions of some geysers was gradually increasing. For example, the eruption interval of Bridal Veil Geyser increased from about 40 to 60 minutes. The Great Wairakei Geyser stopped erupting in May of 1954 (Thompson 1957), but most other geysers were active for a while longer. As production increased to capacity, Wairakei’s geothermal wells reduced the quantity of deep reservoir water flowing into Geyser Valley (Allis 1981). The hot water flowing into streams from overflowing geysers and hot springs decreased steadily between 1952 and 1958 (Allis 1981). By 1962, 4 of the 9 flowing hot springs ceased to discharge, and the other 5 had decreased flow rates (Glover 1977). In 1964, there was only 1 geyser still playing (Stokes 1991), and by 1967, only 2 springs were still discharging. By 1968, the groundwater fell to a point where the geysers completely ceased to play, and the discharge of hot springs stopped. All of these surface features became extinct, including 22 geysers. The activity at Geyser Valley had changed from mainly active geysers and flowing springs to steam-heated, nonflowing pools and mud pools, fumaroles, and empty geyser basins (Glover 1977). Without playing geysers, the area needed a new name. Geyser Valley was renamed the ‘‘Wairakei Natural Thermal Valley.’’ The remaining hydrothermal features were limited to steaming ground, and steam

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heated mud-pools. Presently, the only evidence that geysers once played here are the rapidly weathering, fossil geyser cones (Simmons and Browne 1991). Moreover, many of the hydrothermal features in the Waiora Valley were obliterated during the construction of the geothermal well field. The Waiora Valley was renamed ‘‘Bore Valley.’’ A more detailed ex post facto analysis revealed that the extinction of the hydrothermal features at Geyser Valley was almost certainly caused by Wairakei well withdrawal. First, natural variation before geothermal well production was minimal. Surveys completed between 1888 and the 1920s indicated that there was little natural change in the surface features of the Wairakei area, and only minor changes between the 1930s and 1950s (Glover 1977). The remarkable change in geyser and hot spring activity began in 1951, shortly after the Wairakei wells were drilled. Moreover, the sequence of events at declining hot springs followed a distinct pattern. At first, there was a marked decrease in geothermal water emanating from springs at the margins of Geyser Valley, and from the springs at highest elevations (Glover 1977). A similar pattern of hydrothermal feature decline would occur later at Whakarewarewa (discussed later). Heat flow at Geyser Valley was reduced, but steamheated activity increased in the west and south (Allis 1981), and also later in the Taupo industrial area to the east. For example, by 1964, at Karapiti, about 2 km south of the Wairakei geothermal well field, heat output had increased about 10-fold. The Karapiti fumarole, which was first described in 1864, was the only major fumarole in the area prior to geothermal well withdrawal. It discharged large volumes of superheated steam, but, in 1973, it was extinguished when the vent collapsed (Axtmann 1975; Simmons and Browne 1991). However, the pressure reduction in the geothermal reservoir had stimulated new fumaroles. Beginning in 1954, and continuing spasmodically, there were outbreaks of large fumaroles, and more than 17 hydrothermal eruptions (Allis 1981). Some hydrothermal eruptions blasted craters as large as 1000 m2. A large eruption in 1983 reached 60 m in height, and ejected about 1000 to 2000 m3 of earth material from its crater (Allis 1984). The increased energy loss from hydrothermal eruptions that were induced by geothermal well withdrawal is estimated to be about 90 MW, which is comparable to the heat used at the Wairakei power station (Allis 1981), and can be considered wasted energy (Gresham and others 1983). Geyser Valley was proximate to the Wairakei geothermal wells. However, the quenching of the geysers and hot springs at the Spa geyser basin was

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rather unexpected given its relatively large distance from the well field. The Spa geyser basin was located about 5 km south of the Wairakei production wells. The initial decline of the Spa geysers was caused by the artificial lowering of the Waikato River at the control gate near the outlet of Lake Taupo (discussed earlier), but it was the Wairakei geothermal well withdrawal that finally lowered the boiling chloride water sufficiently to permanently quench the geysers. Eventually, the radius of the Wairakei geothermal well impacts extended up to at least 9 km. The hot springs at Onekeneke (behind the Terraces Hotel), located about 9 km from Wairakei, also failed and dried up. The failure of hydrothermal features at the Spa and Onekeneke demonstrated that the withdrawal of geothermal wells is capable of permanently quenching geysers and hot springs from afar. A reasonable precaution would be to prevent all geothermal well withdrawal within the greater region supplying geysers and/or important hot springs, especially where basins might be interconnected. The challenge is to predict a minimum safe distance for geothermal well placement, given that any artificial withdrawal from a stable geothermal system must affect natural surface heat flow. As the geothermal reservoir pressure and temperature declined over time, so did the output of Wairakei’s production wells. Some of the shallower wells began to draw directly from the steam zone, which contributed to the pressure decline (Allis 1981). Increasing the number of production wells is the typical response to the inevitable decline in the geothermal field, which can place additional demands on the reservoir and any nearby surface features. After 1995, 5 new production wells were drilled at Wairakei, and with the addition of a small turbine, capacity was increased by about 4% despite the geothermal field decline (Huttrer 2001). In 1996, 5 reinjection wells were drilled (Huttrer 2001), and now about 30–50% of the production liquid is reinjected, which has slightly increased the geothermal pressure (Bromley 2003).

Phase 6. Engineering Lessons Learned—Ohaaki Power Station Wairakei represented New Zealand’s first attempt at geothermal power station design. At the time, geothermal engineering was in a fledgling state. Therefore, development was intentionally sited among important geyser basins because the hydrothermal features indicated a good prospect for an abundant supply of geothermal water. Little was known at the time about the potential negative impacts of well withdrawal on

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geysers. However, the lesson was adequately learned at Wairakei, so when the time came to develop New Zealand’s second geothermal power station, the Ohaaki Geothermal Field was chosen. Ohaaki had few hydrothermal features and only one geyser that erupted infrequently (Simmons and Browne 1991). However, among the few surface features was the Ohaaki Pool (800 m2), which was considered to be among the most beautiful large hot springs in New Zealand. Unfortunately, the chloride water discharge of Ohaaki Pool fell considerably after the geothermal well field went into production, then the natural flow was cemented off and replaced with runoff from a geothermal well (Simmons and Browne 1991; Waikato Regional Council 1991). The sinter apron was also irreversibly damaged.

Phase 7. Drowning of Geysers at Orakeikorako The 1.8 km2 Orakeikorako Geothermal Field is located on the banks of the Waikato River about halfway between Rotorua and Taupo (Fig. 1). Orakeikorako contained more than 1000 springs (Lloyd 1972; Simmons and Browne 1991), and had the largest number of geysers (91) of any thermal area in New Zealand (Houghton and others 1980). In 1961, the filling of Lake Ohakuri, a hydroelectric reservoir, raised Waikato River at Orakeikorako by about 18 m, permanently drowning about 75% of the hot springs, and most geysers and sinter terraces (Simmons and Browne 1991; Waikato Regional Council 1991). As the level of Lake Ohakuri slowly rose, the last eruption of submerging geysers could be observed. The drowning of geysers and hot springs at Orakeikorako is remembered as one of the greatest environmental losses in the history of New Zealand.

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heating, 7 major hotels, 67 motels, and various Government departments, hospitals, and schools were also heated with geothermal energy. At the height of Rotorua’s geothermal development, there were more than 900 geothermal wells (Ministry of Energy 1986). The residents of Rotorua ascribed several benefits to geothermal home heating. First, geothermal wells provided relatively low cost heat, thus increasing property values (BPRC 1994). Royalty fees were not instituted until the mid-1980s (discussed later). Therefore, the early tradition allowed residents to tap geothermal heat without paying any resource fees (Ministry of Energy 1986). Second, many residents ascribed a lifestyle enhancement to geothermal heat. Geothermal heating systems were thought to provide high comfort levels all year long. In fact, many elderly people relocated to Rotorua in order to take advantage of the moist heat. The typical domestic geothermal well was about 100 m deep, and was constructed with a 100-mm-diameter steel casing to seal off the shallow groundwater. The production wells have heat exchangers to transfer the heat of the geothermal water to a secondary hot water circuit. The heat exchange process is recommended because poisonous hydrogen sulphide (H2S) gas might escape into the home if the corrosive geothermal fluid is circulated directly. Most of the geothermal wells in Rotorua were constructed and maintained by individuals using private funds. In most cases, the heating systems were installed at minimum cost, and were inefficient. A typical geothermal well could provide heat for more than 30 dwellings, but in 1985, most wells provided heat for only about 8. Reinjection techniques were not used in the early stages of development (Ministry of Energy 1985).

Phase 9. Crisis in Rotorua—Decline of Geysers and Hot Springs Phase 8. Geothermal Energy for Domestic and Commercial Heating A portion of Rotorua City was built over the 18 km2 Rotorua Geothermal Field, including the business district and the southern suburbs. The earliest attempts to tap the geothermal resource used shallow wells to supplement spa pools with hot mineral water. Later, in the 1930s, geothermal energy was tapped to heat a few homes by constructing shallow geothermal wells to extract hot water for heating systems (Houghton and others 1980). Domestic well drilling continued throughout the 1940s, and increased rapidly in the 1950s (Ministry of Energy 1986). In addition to home

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The decline of hydrothermal features at Government Gardens, Rotorua, in the 1930–1940s (date not reliably recorded) was most likely caused, or exacerbated by, human activities. The Rachel Spring and Malfroy Geysers, which were tapped to supply nearby spa baths, eventually failed (Gresham and others 1983; Ministry of Energy 1986). It is not certain that Malfroy Geysers failed solely because of withdrawal of hot water for the spa pools. It is also possible that maintenance was inadequate. However, Malfroy’s engineering work on the springs (Malfroy 1891) was originally undertaken because the spring’s natural overflow had failed, which was used to supply the

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Blue Bath (a spa bath). In the case of the nearby Rachel Spring, its natural discharge failed, and it was pumped, and natural overflow did reoccur several times during the past 30 years. Recently, the water became turbid, perhaps indicating an underground collapse. We will probably never know the exact cause of the failure of these hydrothermal features, but their demise was an early indication of a much greater crisis to come. A few decades later, in the 1960s, a slight decline in other surface hydrothermal features began in the Rotorua area. The cumulative impact of the many small, domestic heating wells was causing reduced discharge and heat content of chloride water at Whakarewarewa (Waikato Regional Council 1991). In 1985, the estimated total maximum mass withdrawn from Rotorua’s geothermal wells was estimated to be 32,000 tons/day in winter, and 25,000 tons/day in summer. The higher well withdrawal during the winter season was producing observable seasonal change in aquifer pressure, with decline in autumn and recovery in spring (Ministry of Energy 1986). Overall, the wells removed about 40% more heat than the natural heat flow at Whakarewarewa (Ministry of Energy 1986). Moreover, the water level of the geothermal reservoir subsided by up to 5 m in some areas, including a decline of about 2 m at Whakarewarewa (Ministry of Energy 1985). As the rate of geothermal well withdrawal increased, hot springs began to fail at Whakarewarewa. It was not until 1979 that the real importance of the decline was realized. In that year, 2 major hot springs—Parekohoru and Korotiotio—failed. The water level dropped suddenly, causing a total change in the character of the springs (Ministry of Energy 1986). Between 1967 and 1969, the Whakarewarewa hot springs were mapped in detail and heat flows were estimated (Lloyd 1975), and heat flows were estimated again between 1984 and 1985. Between these 2 surveys, there was a sharp decline in the water level of many of the chloride springs. Of 63 boiling features in 1969, only 38 were still boiling in 1984. There were 16 active geysers in 1969, but by 1984, only 4 could be relied upon to erupt every day. Today, geyser activity at Whakarewarewa is restricted to Geyser Flat, a 6000 m2 tract of sinterencrusted hot ground (Lloyd 1975). The 4 main geysers of Geyser Flat are really multiple vents of a single geyser system, and include Pohutu, Prince of Wales Feather, Te Horu and Waikorohihi (Ministry of Energy 1985). Pohutu Geyser is perhaps the most famous geyser remaining in New Zealand. These geysers are the last remaining concentration of geysers anywhere in New Zealand (Turner 1985).

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The sequence of geyser decline at Whakarewarewa was similar to that observed at Geyser Valley where the first chloride features to be negatively impacted by the Wairakei geothermal wells were located at the highest elevations along the valley walls and at the margin of the field. At Whakarewarewa, the first major geyser to fail was Waikite Geyser (Fig. 3). Waikite was sited at the highest elevation of any major feature discharging chloride water at Whakarewarewa. The decline of Papakura Geyser, located at the southern boundary of Whakarewarewa, was also consistent with the pattern of early impacts occurring at the margin of the field. Papakura Geyser was an important attraction because it continuously splashed water 5 m into the air. Papakura’s eruptions faltered in March 1979, and finally ceased a month later (Turner 1985). The remaining geysers at Geyser Flat were also eventually affected by geothermal well withdrawal (Allis and Lumb 1992). After 1982, the eruptions of Pohutu Geyser were often very short (5 to 10 minutes). Then, in 1986, it was noted that ‘‘full column’’ eruptions degenerated into low-energy, splashing displays after the first 2 to 5 minutes (Allis and Lumb 1992). Te Horu Geyser (next to Pohutu) stopped overflowing and erupting in 1972, and by 1987 its water level had fallen several meters. Waikorohihi Geyser (also near Pohutu) exhibited unusually long periods of dormancy in 1985 and 1986 (Allis and Lumb 1992). During the same period, many of Whakarewarewa’s chloride hydrothermal features acted abnormally or failed outright. Chloride springs at Whakarewarewa are concentrated at Whakarewarewa Village, Roto-a-Tamaheke (a large hot lakelet east of Whakarewarewa Village), Geyser Flat, and near Waikite and Papakura Geysers (Fig. 4) (Lloyd 1975). The decline of these chloride springs was characterized by falling water levels, dilution, and cooling (Ministry of Energy 1985). Korotiotio (Oil Bath Spring) ceased in 1979, and 2 small hydrothermal eruptions occurred in September and October of that year. Parekohoru was another continuously reliable spring. It was used by the Maori as their main cooking pool in Whakarewarewa Village, and the overflow, combined with Korotiotio, was channeled to the baths (Lloyd 1975). The fizzy ebullition and boiling surges that made Parekohoru (also called Champagne Pool) famous ceased by 1979, and the spring ceased overflowing in 1986 (Cody and Scott 2005). A third group of chloride springs emerged through the bed of Te Roto-a-Tamaheke at the northeast margin of Whakarewarewa, and clustered around its western and northern shores (Lloyd 1975). The once popular Spout Baths were located here, but fell into disrepair and were demolished after the

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springs became dormant in 1942, and water levels and temperatures remained low for 10 years (Lloyd 1975). Reliable discharge from the springs resumed in 1958 (Turner 1985). However, in June 1982, it was noticed that the outflow from one of the outlets had ceased, and continuous discharge did not resume until November—5 months later (Turner 1985). Despite historic natural lapses in discharge, Turner (1985) suggested a connection between the failure of these springs and the drilling of a new geothermal well in 1982 at the nearby Forest Research Institute. It seemed likely that the cumulative well withdrawal in Rotorua had reduced the geothermal pressure at Whakarewarewa to such an extent that the drilling of a single additional well at the nearby Forestry Institute might have caused the observable impacts on the local hot springs (Turner 1985). There was concern that the pattern of decline at Wairakei Geyser Valley, with hydrothermal features failing first at the margin of the field followed soon thereafter by quenching of the remaining hot springs and geysers might be indicative of the sequence of decline in any geothermal system (Turner 1985). If so, the imminent failure of the geysers at Geyser Flat was to be expected unless the implicated geothermal wells were closed (Turner 1985). It is important to note that the prediction of imminent geyser failure at Geyser Flat, which was extrapolated from the observed sequence of hydrothermal feature extinction at Geyser Valley, was complicated by the characteristic irregularity of geyser systems. An important lesson is that scientific uncertainty will inevitably be associated with identifying the initial artificial decline of geysers, and uncovering the ‘‘cause and effect’’ of decline as development impacts commingle with natural variability. The threshold of rapid geyser decline is unpredictable, and small additions to geothermal well withdrawal might trigger irreversible impacts. Therefore, extraordinary precaution is needed to avoid geothermal well withdrawal that might compete with the water and/or heat supply of important hydrothermal features.

Phase 10. Emerging Movement for Geyser Conservation The continuing decline of geysers and hot springs at Whakarewarewa stimulated the conclusion that urgent action was needed to develop a conservation policy for the remaining important hydrothermal features. In 1979, the Nature Conservation Council approached the Geological Society of New Zealand about the lack of a clear policy on the use of geothermal resources. In

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response, both organizations began to lobby the Government for conservation measures, and the Geological Society prepared a white paper, ‘‘The Preservation of Hydrothermal System Features of Scientific and Other Interest’’ (Houghton and others 1980). The White Paper proposed a tiered classification that, for the first time, called for the active protection of important hydrothermal areas. The proposed classification was reasonably balanced in that it recognized the need to develop some ‘‘less important’’ areas. A modified version of the Geological Society proposal was adopted in 1983 when the Government ‘‘Commission on the Environment’’ developed a hydrothermal management strategy based on the concept that ‘‘if the protection of hot springs, geysers and other features were to be achieved, other uses must be subordinate.’’ Government policy was, therefore, modified to exclude large-scale energy development from areas where hydrothermal features were to be permanently protected (Gresham and others 1983).

Phase 11. Government Response to the Crisis in Rotorua The Geothermal Energy Act 1953 required geothermal well owners to obtain licenses (Gordon 2005). In 1967, the Government transferred its geothermal management authority in Rotorua to the City Council (now District Council) under the ‘‘Rotorua City Geothermal Empowering Act.’’ The Empowering Act allowed the City Council to issue licenses and make bylaws for the management of local geothermal wells. However, despite the Government’s attempt to stimulate local geothermal management, the result was a failure. Rotorua had managerial control for 19 years, but no geothermal licenses were issued, and there was little or no control on new well drilling (BPRC 1994). Development progressed with no regard for the sustainability of the geothermal resource or hydrothermal features (Gordon 2005). It is important to note that the extinction of geysers and hot springs at Wairakei Geyser Valley and the Spa geyser basin was unprecedented, but the potential negative impacts of geothermal well withdrawal on hydrothermal features were known about a decade before the ‘‘crisis’’ at the Rotorua Geothermal Field. The noticeable decline and failure of some hydrothermal features in Rotorua, especially the negative impact on geysers at Whakarewarewa, caused the Government to conclude that local control of geothermal management was inadequate (Gordon 2005). The ‘‘crisis’’ dictated that the Government return to formal

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involvement (BPRC 1994). Together, the Government’s Minister of Energy and the Rotorua District Council developed guidelines for geothermal well drilling in Rotorua. The new rules included a ‘‘ban’’ on drilling within a 1.5-km radius of Pohutu Geyser, except for replacement wells (Fig. 7). The Government also created the ‘‘Rotorua Geothermal Monitoring Programme,’’ which was to monitor the geothermal reservoir status for 2 years beginning in 1982 (Ministry of Energy 1986; Allis and Lumb 1992). In 1983, the Minister of Energy set up a Task Force to look at ways to immediately reduce geothermal well withdrawal and improve efficiency (Ministry of Energy 1986). By 1985, it was estimated that the groundwater level of the Rotorua Geothermal Field had declined 2 to 4 m (Allis and Lumb 1992). By the winter of 1986, aquifer pressures had fallen to their lowest levels since the

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monitoring began, despite the widespread publicity on the need for conservation (Allis and Lumb 1992). The geothermal field appeared to be rapidly deteriorating, which resulted in a recommendation that ‘‘urgent action’’ was needed to save the geysers at Whakarewarewa (Allis and Lumb 1992). Scientists were advising that the decline of hydrothermal features had reached a ‘‘crisis’’ proportion, and that immediate action was needed to protect the geysers from extinction. Given the need to act decisively, the Government responded by rescinding local authority for Rotorua’s geothermal management, and applied direct regulations to force an overall reduction in well withdrawal near Whakarewarewa. On October 2, 1986, the Minister of Energy signed ‘‘Ministerial Directive 1986,’’ which revoked Rotorua City Council’s delegated powers under the Rotorua City Geothermal Empowering

Fig. 7 Domestic and commercial geothermal heating wells in Rotorua City ca. 1985, and the 1.5-kmradius geothermal well exclusion zone instituted by the Government to save the geysers at Whakarewarewa (after Allis and Lumb 1992)

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Act 1967. Then, on October 6, 1986, the Government invoked its statutory authority under ‘‘Cabinet Directive 1986’’ (Cabinet Development and Marketing Committee, Cabinet), which again revoked the City Council’s authority to manage geothermal development. Also, in a major new initiative, the Cabinet Directive ordered the ‘‘closure’’ of all geothermal wells (about 120 wells) within a 1.5-km radius of Pohutu Geyser. The closure area is now known as the ‘‘Rotorua Geothermal Exclusion Zone’’ (Fig. 7). Well closure was to be accomplished by December 1, 1986, which represented a nearly immediate closure of the wells (BPRC 1994). The goal of the Government’s well closure initiative was to prevent further decline of the remaining geysers and avoid pressure increase across the geothermal field. Over the years, new homes were built on geothermally unstable ground. Any reservoir pressure increase after well closure might have induced hydrothermal eruptions. Hydrothermal eruptions are known hazards that have the potential to cause major damage to houses and commercial buildings. Therefore, natural hazard and risk assessment adds to the cost of any major reduction in well withdrawal (BPRC 1991). In addition to the geothermal well–closure program, the Government required that wells outside the specified 1.5-km radius would need to be licensed, there were new equipment requirements, and a royalty charge was applied for geothermal withdrawal (BPRC 1991). The royalties applied only to geothermal users in Rotorua. The royalties were not trivial—the new fees imposed an additional annual cost of between NZ$12,000 and NZ$52,000 on well users. The royalty charges were deliberately set at a high level in order to encourage efficient use, and encourage conservation measures or reinjection techniques. If geothermal users adopted conservation measures, they could receive lower royalty fees (BPRC 1994).

Phase 12. Public Protest of Geothermal Well Closures in Rotorua The Government’s resolve to protect the remaining geysers at Whakarewarewa was popular across most of New Zealand, but the well closure program was highly controversial in Rotorua. The closure of wells was viewed locally as a radical policy change. In retrospect, 2 factors contributed to the Government’s abrupt implementation of these new environmental regulations: (1) the nearly two-decade-long failure of Rotorua to adopt incremental geothermal conservation measures, and (2) the Government’s long patience

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with local inaction. When the crisis stage required decisive rulemaking to protect the remaining geysers, the Government’s reward was considerable local resentment. It is important to note that voluntary conservation was not a successful remedy for protecting the geothermal resource, or the hydrothermal features at Whakarewarewa. Many Rotorua geothermal users were slow to adopt voluntary conservation measures because of perceived historic rights and resistance to change. Historically, access to Rotorua’s geothermal heat was essentially free, and use patterns developed into a tradition over a period of decades. The geothermal lifestyle attracted a self-selected group of committed adherents and defenders of the tradition. Even after the Government declared a ‘‘crisis,’’ the well closure was perceived as an unjustified taking of important aspects of Rotorua’s geothermal lifestyle. At the height of frustration, tensions in Rotorua reached near riot status (Vercoe 1994). Public resistance to the Government’s well-closure program was organized by the ‘‘Rotorua Geothermal Users Association.’’ Despite the friction between the local residents and the Government, there seemed to be mutual agreement on the need to preserve the remaining geysers. Nonetheless, debate raged on the appropriate degree of change, especially regarding domestic heating systems. Vercoe (1994) summarized the issues that contributed to the negative local perception of the Government’s new geothermal management regulations. Rotorua geothermal users cited scientific uncertainty and reminded the Government that Whakarewarewa underwent natural dormant phases, including a major period of decline in the early 1900s. Therefore, they argued that low rainfall rather than geothermal wells might be causing geyser decline (Vercoe 1994). Many users thought that the Government’s 2-year geothermal monitoring program was far too short and might result in premature conclusions. Moreover, next to Pohutu Geyser, one of the Government’s monitoring stations was located just 250 m from a rogue well’s massive discharge—enough to heat 300 homes. The local users preferred a more gradual approach, and offered up to an 80% reduction in well withdrawal, amalgamating user groups and using reinjection (Vercoe 1994). The Government was also reminded that it had sanctioned private geothermal investment of NZ$48 million in Rotorua over several decades, and some hotels were located in Rotorua to take advantage of spa pools (Vercoe 1994). There was no proposed compensation for any economic losses. Moreover, some users thought that it was not necessary to close low-pressure domes-

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tic geothermal wells, if high-pressure Government wells were closed instead at the Forestry Research Institute, the International Hotel, the Whakarewarewa Primary School, and the Waiariki Community College (Vercoe 1994). In the end, many Rotorua residents were left to believe that the Government handled the crisis poorly, even though it was the local control that actually failed to protect the local geysers and hot springs. The lesson is clear—when the goal is to preserve geysers, competing consumptive uses for geothermal water should be prevented at the outset. Otherwise, local adherents to the established use become dedicated advocates for the status quo, complete with organized resistance to change, and, ultimately, organized disenchantment with government remedies.

Phase 13. A Mixed Recovery of Hydrothermal Features in Rotorua In Rotorua, most of the geothermal wells within 1.5 km of Pohutu Geyser were closed by 1987, but resistance from well users, including legal challenges, delayed some well closures until mid-1988. Overall, the Government’s well closure and royalty charge program reduced the number of geothermal wells from a preclosure total of 376 wells (Grant-Taylor and O’Shaughnessy 1992) to 140-well production sites by 2005 (net after backup and reinjection wells are subtracted) (O’Shaughnessy 2005). In 2005, about half of the geothermal wells were domestic, with the remainder serving commercial establishments. Between 1985 and 2005, net geothermal withdrawal (production minus reinjection) was reduced from 27,500 tons/day to 970 tons/day (O’Shaughnessy 2005). Much of the decrease in net withdrawal is accounted for by increased reinjection, which was required where feasible and safe by July 1, 2002. By 2005, about 90% of Rotorua’s geothermal well withdrawal was reinjected as a conservation measure (O’Shaughnessy 2005). As for the future, it is expected that few new wells will be drilled because the economics of using local geothermal energy is extremely marginal (O’Shaughnessy 2005). Also, the economic incentives that were put into place to protect hydrothermal features created some unintended social costs and adjustments in geothermal use patterns. For example, the elderly and average families in Rotorua found it difficult to take advantage of the economic incentives to induce conservation, so there has been a shift from domestic to commercial geothermal use (O’Shaughnessy 2000).

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The fluid levels in the geothermal reservoir improved shortly after the well closures. Late in 1987, most of the monitoring wells showed an increase in water level between 1 and 2 m, noteworthy pressure gains were recorded by the end of 1988, and by about 1992, water levels in the geothermal field fluctuated seasonally around an apparently uniform level (Gordon 2005). After the well closures, outflow of some hot springs increased at Whakarewarewa. By 1989, the famous Parekohoru hot spring (that faltered in 1979 and ceased in 1986) resumed its boiling overflow surges, and has maintained overflow every 1–2 hours since the late 1990s (Cody and Scott 2005). The Korotiotio hot spring, which ceased reliable overflows in 1979 and ceased entirely in 1980, has never resumed overflow—the vents might have been damaged by hydrothermal eruptions (Cody and Scott 2005). By 1992, some surface hydrothermal features had increased in activity, and some dormant springs resumed flow. The lakelet Roto-a-Tamaheke (that ceased flowing in 1982) increased its outflow by about 50% during 1986 and 1987, but heat recovery was more gradual (Allis and Lumb 1992). However, more recently, Roto-a-Tamaheke has not followed the trend of recovery. In March 1996, the Ororea Group of springs ceased boiling and flowing, and in March 2001, all of the western lakeside springs abruptly ceased, and other associated springs along the northern and western margins cooled and fell below overflow level (Cody and Scott 2005). The cause is unknown. By 1989, Pohutu Geyser resumed longer duration, full-column, high-energy eruptions (Cody and Lumb 1992), a trend that progressively developed through 2001 (Cody and Scott 2005). The vent of Te Horu Geyser is located just south of Pohutu. Te Horu ceased eruptions in about 1972, and during the 1980s there was no overflow from the vent. However, during the late 1990s, the water level in Te Horu’s vent rose progressively, and in 2000, overflow resumed (Cody and Scott 2005). Nonetheless, the overflow temperatures have remained below boiling and Te Horu has not resumed eruptions. In 1987, the dormant Kereru Geyser began erupting. Okianga Geyser eruptions were rare in the early 1980s, but it continued to play throughout the late 1990s. Small fissures and flowing vents opened up by 1999, and geysering ceased. However, Okianga began erupting again in 2004 (Cody and Scott 2005). It is suspected that the Okianga Geyser might be displaying natural variability rather than a response to geothermal field recovery. Mahanga Geyser, located 20 m south of Pohutu Geyser, illustrates the complexity of interpretation following the geothermal well closure program. Mahanga is an example of recent geyser

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decline and dormancy. In 1999, Mahanga became erratic, with geysering activity decreasing progressively. By 2001, Mahanga’s eruptions became rare, then ceased, and no eruptions have been observed since then (Cody and Scott 2005). Waikorohihi Geyser is another feature that has declined from historically active status (typically with 12–20 eruptions per day), then decline and long dormancies starting in 1986, and rare eruptions since 2001 (Cody and Scott 2005). Therefore, Waikorohihi Geyser has not recovered. Dye tracers have shown that Waikorohihi is interconnected with the Pohutu Geyser system at shallow depth. Therefore, recovery of the Pohutu system does not appear to be complete if eruptions at Waikorohihi Geyser still cannot be supported, or perhaps subterranean changes in the plumbing have occurred. All of the large extinct geysers (Papakura, Wairoa, Waikite, and Ororea) show no signs of recovery (Cody and Scott 2005). The uncertainty associated with documenting the recovery of the hydrothermal features at Whakarewarewa suggests that more comprehensive field monitoring and research would be beneficial. More comprehensive monitoring would also provide early warning of unexpected negative impacts that might be caused by ongoing geothermal well withdrawal in Rotorua, especially during future climate change. The response to geothermal well closure in other parts of the Rotorua Geothermal Field is variable. Rachel Spring in Government Gardens is the largest hot spring in the Rotorua area, but has rarely overflowed or boiled since 1988. After the well closure program, it has fluctuated from flowing to nonflowing, but the water level has recently fallen to about 1 m below overflow with little change in temperature (Cody and Scott 2005). However, in the northern and northwestern part of the Rotorua Geothermal Field, there has been consistent recovery of surface features. For instance, the thermal area at Kuirau Park exhibited increased boiling outflows after a long period of dormancy between 1989 and 2001 (Cody and Scott 2005). In 2001, a large hydrothermal eruption occurred at Kuirau Park. The eruption lasted about 4 minutes with a column height of about 100 m, and ejected about 1200 m3 of muddy debris and boulders as big as 1 m in diameter (Cody and Scott 2005). The recovery of some surface features is evidence that the conservation of mass and energy by reducing geothermal well withdrawal was important in sustaining some hot springs, and increasing the energy of the remaining geysers (Gordon 2005). However, recovery is far from complete given that no extinct geysers have recovered. Some other hydrothermal features also failed to recover, and the chloride water supply to

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Whakarewarewa is still considerably less than before the geothermal well closure program. Therefore, the success of the well closure program—although laudatory—remains limited, and, apparently, insufficient to reestablish the lost geysers or stimulate new ones. The Government recognized the need for planned management of the Rotorua Geothermal Field. Under the authority of the Resource Management Act 1991, the ‘‘Rotorua Geothermal Regional Plan’’ was adopted in 1994 (BPRC 1994). The Regional Plan proposed to control the extraction and discharge of all geothermal fluids through the water rights procedure of regional water boards, and the licensing responsibility of the Ministry of Energy (BPRC 1991). Some of the plan’s key features are (1) maintaining the 1.5-km radius fluid withdrawal exclusion zone around Pohutu Geyser; (2) no net increase in withdrawal from the geothermal field as of 1992; (3) reinjection of all withdrawn fluids; (4) setting water levels in the geothermal aquifer to sustain and protect surface resources; and (5) protection of surface features from physical destruction (Gordon 2005). The regional management plan for the Rotorua Geothermal Field is due for review in 2005.

Phase 14. Geothermal Modeling in Rotorua and Future Planning Computer modeling generates predictions about the performance of the geothermal reservoir based on theories of subsurface reservoir behavior under specified assumptions. Simulations can then be tested against actual conditions taken from well-monitoring data in Rotorua and changes in resource use (Gordon 2005). A series of increasingly sophisticated models have been developed, with a recent update in 2004. The updated model predicts that with the current geothermal production and reinjection, the Rotorua Geothermal Field pressure and outflow will be maintained in a ‘‘stable dynamic state,’’ with small changes due to climate variation (Burnell and Kissling 2005). Computer models are usually implemented as tools to predict the impacts of additional future development with the goal being to maximize the sustained yield. In anticipation of a pending update of the Rotorua Geothermal Management Plan in 2005, the Government sanctioned an update of the 2004 reservoir model to simulate the effects on Rotorua’s hydrothermal features from 19 geothermal energydevelopment scenarios. All of the scenarios included an increase in well withdrawal of fluid and heat across the Rotorua Geothermal Field (Burnell and Kissling

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2005). These scenarios considered geothermal well withdrawal increases up to 20%, and some scenarios even considered up to 20% increases in well production within the 1.5-km exclusion zone around Pohutu Geyser. Any plan to increase geothermal well development that implies a negative impact on surface hydrothermal features is not likely to be adopted by the Government (Burnell and Kissling 2005). However, given the loss of important geysers and hot springs in Rotorua’s past development history, and the increasing value of the remaining surface hydrothermal features to the local economy and to New Zealand’s heritage, it is a troubling abandonment of precaution to consider new geothermal development in Rotorua, especially in the exclusion zone that protects Whakarewarewa. Although computer models can be refined, the resulting predictions are not likely to be able to anticipate environmental variability over decade-long planning horizons. Therefore, geyser and hot spring preservation regulations should provide a considerable margin for error. Trying to maximize the sustained yield of geothermal energy resources in the vicinity of important hydrothermal features is fraught with peril—much of it irreversible.

Conclusions Geyser basins rely on a relatively delicate arrangement of geologic, thermal, and hydrologic conditions, which are easily impacted by human development. The rarity of geyser basins, and their increasing recreational, economic, and scientific importance, make it imperative that the world’s remaining geysers be permanently protected. The extinction of more than 100 geysers in New Zealand is convincing evidence that strong regulations are required at the outset to prevent the consumptive use of geothermal water or heat near geyser basins. The experience at the Spa geyser basin demonstrated that lowering the water level of a river is likely to damage streamside geysers. Clearly, the Wairakei geothermal well withdrawal demonstrated that industrial-scale energy development is not compatible with playing geysers. The decline of hydrothermal features at the Spa and Onekeneke demonstrated that the impact of geothermal well withdrawal is capable of radiating many kilometers. The extinction of geysers at Orakeikorako demonstrated that hydroelectric dam development, or any project that permanently raises the water level of a river, is capable of drowning streamside geysers. In Rotorua, the negative impact of numerous domestic and commercial heating wells demonstrated that

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relying on the phased management of future impacts is likely to be a prescription for geyser decline or extinction—complete with dedicated groups opposing change and powerful private, corporate, and government investors arrayed to defend traditional geothermal withdrawal levels. Not a single geyser recovered at Whakarewarewa after geothermal well closures in Rotorua, which demonstrated that geyser quenching is an irreversible commitment. It is generally recognized that the natural surface features of geyser basins, if properly protected from development impacts, are sustainable resources, whereas the useful lifetime of a geothermal well field is only about 50 years. Moreover, there are numerous substitutes for energy production. However, given the inevitable demand for energy, there will probably always be development pressure on New Zealand’s geothermal fields. New geothermal power stations have been constructed, including at Mokai, Kawerau, Ngawha, and Rotokawa, and there are proposed developments at Mangakino and Tauhara (Huttrer 2001). Moreover, in Rotorua, there has been recent public discussion about the recovery of some hydrothermal features, with the implication being that additional geothermal energy development can be reconsidered. However, no extinct geysers at Whakarewarewa have recovered. Acknowledgments The research was generously supported by the School of Geography and Environmental Science at the University of Auckland, New Zealand, and by a sabbatical leave granted by the University of Alaska Fairbanks. I would like to thank the editor and the reviewers of the manuscript. I would like to extend a special thanks to Ronald F. Keam and Edwards F. Lloyd, both geothermal experts in New Zealand, for suggesting valuable and detailed improvements to the manuscript. E. F. Lloyd also provided historic photographs of extinct geysers (Fig. 3).

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