ISSN 00978078, Water Resources, 2013, Vol. 40, No. 6, pp. 573–584. © Pleiades Publishing, Ltd., 2013. Original Russian Text © R.G. Dzhamalov, N.L. Frolova, M.B. Kireeva, 2013, published in Vodnye Resursy, 2013, Vol. 40, No. 6, pp. 544–556.
WATER RESOURCES AND THE REGIME OF WATER BODIES
Current Changes in River Water Regime in the Don River Basin R. G. Dzhamalova, N. L. Frolovab, and M. B. Kireevab a
Water Problems Institute, Russian Academy of Sciences, ul. Gubkina 3, Moscow, 119333 Russia email:
[email protected] b Moscow State University, Moscow, 119991 Russia email:
[email protected] Received April 10, 2013
Abstract—The formation and distribution of presentday water resources under the effect of changing cli mate are studied. Seasonal, annual, and manyyear variations in the regime of springflood and dryseason runoff of rivers with drainage areas from 2000 to 20000 km2, reflecting the zonal landscape–climatic condi tions of runoff formation, are considered. It is shown that various and often contradictory demands of water users to water supply distribution over seasons of the year result in that the entire water management complex depends on not only the total volume of water resources, but also on the water regime characteristics of rivers in different phases of hydrological year. It was established that the climate changes recorded in the recent decades radically change the pattern of space and time variations in runoff characteristics. Keywords: water resources, natural groundwater resources, river runoff, groundwater runoff, runoff regime DOI: 10.1134/S0097807813060043
INTRODUCTION Current changes in the climate and water regime were based on observational data collected at 56 weather stations and 55 gauges. The space and time analysis of runoff over 1988–2008 was based on data of NorthCaucasian Office for Hydrometeorology and Environmental Monitoring. The observational series were divided into the present day period of 1970–2008 and an earlier period of 1936–1969 to make the con clusions about the direction and nature of changes taking place in runoff regime and water resources for mation. The obtained data made it possible to compile a series of maps of water resources and runoff charac teristic estimates with the help of ArcView software package, and to fully analyze the seasonal and annual runoff variations in different phases of water regime with the use of Statistica and Excel software. Variations in meteorological characteristics were analyzed using Roshydromet reports on climate fea tures in RF territory over 2008–2012 years and data presented by RIHMIWDC. The global climate changes on the southern slope of European Russia (ER) manifested themselves, primarily, in the warmer winter and greater total precipitation over the cold season. CLIMATE CHANGES The global climatewarming trend of 1976–2012, which has become slower in the winters in recent years, still can be seen in the Russian territory. The mean growth rate of mean annual temperature for
Russia as a whole (0.43°С/10 years) is about twice that for the global temperature. The major seasonal fea tures of 2012 in Russia are a very warm summer (+1.61°С, the second largest anomaly since 1936) and a warm autumn (+1.78°С, the sixth one from 1936). By their temperature regime, the winters of 2011/2012 in Russia can be divided into two parts: a vast and rel atively warm northern one and a narrow and some what colder southern one. On the average, the sea sonal anomaly of winter temperature is +0.87°С (the 27th in the series since 1936). At the same time, it was very cold in the southern part of ER, especially in the Northern Caucasus, as well as in the Southern Ural, Altai, and Sayany. Conversely, positive anomalies (by 10–15°С) were recorded on the Arctic coast of the Northern Siberia (Yamal, Taimyr, etc.). This winter warming zone persisted over northern areas for three winter months. The anomaly of spring temperature at most stations in 1961–1990 was in excess of the norm and averaged +1.62°С (the 12th anomaly since 1936). Anomalies in excess of the 95% occurrence (up to 4.6°C) were recorded in the southern ER [6, 9]. The increase in air temperature in the cold season in southern ER is most vivid. Statistically reliable increase in the mean coldseason temperatures in 1936– 2008, which was recorded at more than half of weather sta tions considered, averaged 0.35°С/10 years. The stron gest increase was recorded in the basins of the Middle Don and the Severskii Donets. The warming is accom panied by an increase in the sum of positive tempera tures over the cold period by 20% on the average.
573
574
DZHAMALOV et al.
Statistical analysis of the time dynamics of total precipitation over the cold season since 1936 to 2010 has shown a significant decrease in the variance at 33 weather stations out of 57 and an increase in mean values at 14 weather stations. The increasing trend in winter precipitation is confirmed by Spearman test (for 35 weather stations out of 57). The mean coeffi cient of linear trend was 9.2 mm/10 years. The observed slight increase in warmseason precipitation is statistically insignificant. The total coldseason precipitation determines February snow storage. Water reserves in the snow cover in 1966–2006 in the northern part of the Don basin are on the average 70–80 mm; those reserves decrease to 20–50 mm in the southern and southeast ern direction. Analysis of time variations in snow stor age failed to reveal statistically reliable changes. This is due to the strong effect of thaws and an increase in the liquid component of atmospheric precipitation in cold season against the background of a slight increase in its total. The dates of change of climate seasons in the southern ER also change. The mean date of the stable passage to negative temperature shifts from early November in the north to early December in the southeast. Since the early 1990s, some weather sta tions show a clear tendency toward a shift of this date toward later times. On the other hand, the mean dates of the beginning of fiveday frostfree period vary over the territory of the Don basin from midFebruary in the southeast to early April in the north. A significant increase in the variance of this characteristic and a shift of this date toward earlier dates by 12 days on the average is typical of 50% of weather stations. WATER RESOURCES OF THE SOUTHERN ER The southern regions of ER are large industrial and agricultural agglomerations at the country scale. Water resources form the basis of economy. River runoff reg ulation in this area began as early as the XVIII century. However, the construction of reservoirs as means of active runoff regulation started only in the 1950s. More than 12 thousands of ponds and small reservoirs (the majority of them (67%) are small reservoirs and ponds with the useful storage of less than 1 million m3) and 48 large reservoirs of various purposes with the useful storage of more than 10 million m3 are situated in the Don basin. The rates of water withdrawal for almost all types of water users was decreasing in 2000–2010. The use of fresh water dropped from 5 to 3.2 million m3/year. Agricultural water supply decreased significantly (by a factor of 4), which is comparable with the decrease in water withdrawal for irrigation (by 0.7 km3/year). Par allel to this, the areas of tillage, agricultural lands, and irrigated areas were steadily decreasing in recent 20 years. The largest water intakes in the basin are based on the Tsimlyansk Reservoir.
Water resources deficit in the Don Basin alone is 26.8 million m3/year. The largest water deficiency is recorded in the Voronezh R. basin. Thus, it reaches 81 million m3/year at the gage at Lipetsk City and 66 million m3/year within the reach from Lipetsk to the Voronezh Hydropower System. A small water defi ciency exists also in the Oskol R. at the Starooskol’skii Hydropower System and in the Sal R. Basin (14.4 mil lion m3/year). Water consumption in the Egorlyk R. Basin is three orders of magnitude greater than its maximum allowable value. Notwithstanding the deficiency of water resources in some basins, the entire watereconomic complex of the Don R. Basin receives all water it needs. However, the resources of the river will not be enough if addi tional water demand appears [10]. The volume of river runoff in the basin is estimated at 26.8 km3/year, and the mean annual runoff modulus is relatively low (about 2 L/(s km2). The modulus of annual water discharge, averaged over 1970–2008 for 45 gages, shows zonal variations: from 4.7 in the upper reaches of the Don to 0.6 L/(s km2) on the left bank of the Tsimlyansk Reservoir and the lower reaches of the Don (Fig. 1). The total water resources (mean annual runoff) of the Don R. over the entire observation period were 28.1 according to estimates of 1987 and 26.8 according to estimates before 2005; the authors’ calculations for 1970–2008 yielded an estimate of total water resources of the basin of 22 km3/year. The effect of climatic and anthropogenic factors on variations of the characteristics of annual runoff and water resources in the basin can be evaluated based on the analysis of estimated conventionally natural runoff of the Don [11]. Analysis of runoff characteristics has shown that the main changes in both the runoff itself and total water resources under the effect of anthropo genic activity can be clearly seen downstream of the Tsimlyansk Reservoir. On the other hand, the many year variations of the conventionally natural annual runoff of the Don proper show a slight decreasing trend, while the runoff of the majority of its tributaries is relatively uniform. The dryseason runoff of rivers in the region was characterized by averages over July–September and December–February. The sixmonth average of the dryseason runoff was chosen because it serves as a characteristic of natural groundwater resources and its correct assessment is of particular interest. In accor dance with the accepted approaches, the minimal monthly values of water discharge are evaluated sepa rately for the summer–autumn and winter dry sea sons, i.e., they characterize typical lowwater periods in the runoff regime. Natural resources are a characteristic of groundwa ter replenishment; they reflect its main feature as a renewable underground resource. The normal mean of groundwater recharge less the evaporation and spring WATER RESOURCES
Vol. 40
No. 6
2013
CURRENT CHANGES IN RIVER WATER REGIME 37°
43°
46° Moksha
40° Osetr
53°
3 Bity ug
Sav a
la
1
Vor
3
Uz a
Tsna
one zh
ya M ec ha
a
Med vedi tsa
Zh izd ra Ok a
53°
S
Sur
Ilovlya
ha Zus
Kr as iva
va no Ra
n
a sh Vy
E
Lesnoi Voronezh
Do
W
Vad
Para
Pronya
Vorona
Up a
N
575
2
im Se
an El
3 a sn So
2
Volg ograd
47° koe R
es.
1
Eya
ba Ku n
l. Bo ba La
0
100 km
up Ur
37°
Ves elo vs
a lay Be
lakes Changes in runoff modulus <–50 –50–20 –20–0 0–20 20–50 >50 Countries Russia Ukraine seas
Sal
Tuzlov
in sk ie La ke s
Kalaus
47°
Sa rp
Eg or l yk
Modulus of annual runoff L/(s km2) rivers
Res.
Kh op er
ya stra By
kii D onet s
Tsi ml
Seve rs
Ch ir
.
Don ets
Darkul
Oskol rski i
Aidar
Sev e
a Kalitv
ya na as Kr
40°
43°
Fig. 1. Modulus, L/(s km2), of mean annual runoff in the Don Basin rivers in 1970–2008.
WATER RESOURCES
Vol. 40
No. 6
2013
50°
Res
Aidar
Tamulae
Che rnay a Ka litva
50°
1
Bu zu luk
yan sko e
ver s Se
Oskol
skla Vor
a ay kh Ti
vka
kii Do n
ets
Psel
576
DZHAMALOV et al.
runoff is equal to the groundwater runoff; therefore, in regional estimates, natural groundwater resources are often expressed in terms of mean annual moduli of the dryseason and minimal monthly runoff (in L/(s km2)). Because of the genetic character of natural water resources, their formation conditions are directly related to possible climate changes (observed and fore casted) and manifest themselves in the dynamics of annual and seasonal values of those resources. The effect of longterm climate variations is evaluated by changes in the normal manyyear and minimal monthly values of natural water resources over a 30year and longer period, regarded as representative. The dryseason runoff in the region is not large because it is located in the southern ER in a zone of insufficient moistening. On the average for the Don Basin for 1970–2008, the modulus of dryseason run off (the Don R., Razdorskaya St.) is 1.5 L/(s km2). The mean dryseason modulus steadily decreases from northwest to southeast (Fig. 2). Its largest value (up to 3.3 L/(s km2) was recorded in the northwestern part of the basin on the Krasivaya Mecha R. (Efremov gage). The modulus upstream of Zadonsk T. is 2– 3 L/(s km2), while further downstream it decreases to 1 L/(s km2) (Pavlovsk gage). The comparison of the spatial distribution of the obtained values of dryseason runoff, which charac terizes natural groundwater resources, with their dis tribution according to estimates of the 1960s–1970s shows that, the general patterns of contour lines being similar, they almost everywhere shift southeastward, suggesting an increase in dryseason runoff by a factor of 1.5–2. Thus, according to earlier estimates, the modulus of groundwater runoff in the Severskii Donets basin was 0.3–0.5 L/(s km2), while the presentday estimates yield 1–2 L/(s km2), i.e., the natural groundwater resources in this basin have increased significantly. The changes in dryseason (groundwater) runoff for the absolute majority of rivers in the basin are sta tistically significant. The positive trend is statistically significant at 42 out of 49 examined gages (86%) (Table 1). The increase in the areadistributed recharge of groundwater is confirmed by regular observation data of 1989–2007 on groundwater level (GL) in the “Dokuchaevskii well” in Kamennaya Step, where the groundwater table rose from 7 to 4 m [4, 5]. The mean values of the dryseason runoff increased significantly in 1970–2008 (the growth rate of the modulus was 0.4–0.5 L/(s km2) over 10 years) at the expense of both winter and summer dryseason values. Stable correlation between mean dryseason winter and summer discharges with correlation coefficients of more than 0.65–0.7 was found to exist at all gages under consideration (Fig. 3a).
It is worth mentioning that the value of the drysea son runoff of a year shows a high multiple correlation coefficient (up to 0.75) with the total precipitation over the cold season of the previous year, the total pre cipitation of the cold season two years ago, and the total precipitation for the warm season of the current year (Fig. 3b). No correlation was found to exist between the dryseason runoff and air temperature. The dryseason runoff shows considerable inertia, resulting in high autocorrelation coefficients, which are large up to the lag of 4–5 years. Minimal monthly discharges in rivers of the region are recorded in the summer–autumn and winter dry seasons. In the northwestern part of the basin, they average about 3 L/(s km2), from where they gradually decrease southeastward to 0.3–0.7 L/(s km2) or less (Figs. 4a, 4b). In this case, the summer discharges averaged over 1970–2008 are in 80% of cases (43 out of 50 gages) less than the respective winter values. The changes of characteristics of mean monthly runoff either for winter or for summer period are statistically significant at all gages under study (Table 1). The larg est variations in minimal monthly discharges were recorded in a wide zone extending from southwest to northeast in the middle part of the basin; the transfor mation of water regime of rivers is the largest in this zone. No stable snow cover has formed in winter southeast of this zone since the first half of the XX cen tury up to now, while northwest of this zone, a stable snow cover forms, notwithstanding the considerable current changes in winter temperature regime. Variations of the minimal winter and summer run off moduli are synchronous. In different rivers, the values of the characteristics under study vary in accor dance with the general course with small deviations in the amplitude and with some lag. Linear regression relationships between those two characteristic can be seen at all gages. In rivers of the forest zone, these rela tionships are clear and show correlation coefficients greater than 0.6–0.7, while south of this zone, the relationship between minimal winter and summer runoff moduli becomes weaker and the correlation coefficients decrease to 0.4. For the majority of rivers, the mean monthly runoff moduli over 1970–2008 are greater than those for 1936–1969 by 30–60% (Fig. 5). Their increase is sta tistically significant at 42 gages out of 44 (95%), and an increase in the variance is statistically significant at 37 gages out of 44 (84%) (Table 1). The coefficient of variation of minimal winter runoff moduli for the southeastern part of the basin is 0.2–0.35. The inertia of the minimal summer and winter monthly runoff is reflected in the high values of auto correlation coefficient for successive years. In the majority of rivers, those coefficients are in excess of 0.6, and for some rivers, they reach 0.8. The coeffi cients of autocorrelation for rivers with their high val ues often deteriorate slowly even at a lag of 8–9 years, at which they sometimes are greater than 0.4. WATER RESOURCES
Vol. 40
No. 6
2013
CURRENT CHANGES IN RIVER WATER REGIME 38°
36°
42°
44° 54°
ya M ec ha ez h Voro n
1 Sa va la
ug
52°
Bity
52°
Medv ed
S
Uz a
itsa
2 iva
Vorona
Kr as
E
W a Ok
46°
Lesnoi Voronezh
Do n
3
Tsna
Z
40°
N
d Va
54°
dra hiz
577
1
Se im
a El n
So sn a
Psel
Bu zul uk
Aidar
ii D one ts
Darkul
ersk
Aidar
Sev
ya na as r K
Kh op er
Kalitva
Oskol
50° 2
a Ka litva
50°
0.5 es
Cher nay
ra d R
ol Osk
3
Volgo g
kla
Tamula evka
Ti kh ay a
s V or
Chi r
46°
2 Seve rskii Don et
s
48°
L ie
n Do V ese lov
rivers major rivers Modulus of dryseason runoff, L/(s km2) Changes in dryseason runoff modulus, % –100...–50 –50...⎯20 –20...0 0–20 20–50 50–100 100–250 Countries
1 Tsi mly ans koe R
46° es.
Kalaus
Eg
or
lyk
2
ba Ku n
l. Bo ba La
0
p Uru
36°
sko eR es.
Egorlyk
Russia Urkaine seas
44°
es ak
Tuzlov
46°
sk in rp Sa
0.5
48°
100 km 44°
38°
40°
42°
44°
Fig. 2. Mean dryseason runoff modulus and its changes in the Don Basin in 1970–2008.
Factor analysis makes it possible to evaluate the minimal summer monthly discharge by the runoff depth of spring flood and the mean monthly discharge in October in the previous year. The latter value char WATER RESOURCES
Vol. 40
No. 6
2013
acterizes the autumn moistening and determines the character of runoff losses during spring flood and thus, the minimal summer water discharges: (1) Qmin s (n) = f [y n(n); Q X (n − 1)],
578
DZHAMALOV et al.
The values of statistical criteria for series of mean winter dryseason modulus and minimal monthly runoff of Don Basin rivers in 1936–1969 and 1970–2008 (statistically significant changes are given in bold type) Statistical tests River–gage
Number of years
Spearman
Fisher
Student
dryseason runoff/minimal monthly runoff Don Zadonsk
78
0.74/10.21
2.15/4.14
–4.86/–4.74
Liski
126
0.51/6.52
1.4/4.17
–6.06/–6.48
Pavlovsk
125
0.54/8.38
1.82/3.91
–5.52/–7.85
Kazanskaya
105
0.66/12.83
1.94/6
–3.79/–5.15
Belyaevskii
56
0.7/11.9
1.38/5.71
–3.11/–5.03
Kalach
123
0.47/7.1
1.26/3.41
–4.71/–7.73
TsGU
124
0.51/7.6
1.54/5.05
–4.94/–7.51
80
0.69/11.75
0.51/1.42
–4.49/–6.67
49
0.54/4.66
5.44/16.96
–2.07/–2.23
Elets
61
0.47/7.15
1.23/8.89
–2.66/–4.31
Belomestnaya
57
0.51/5.29
2.14/4.03
–2.85/–3.2
Voronezh–Lipetsk 2
73
0.8/8.48
4.32/4.24
–6.18/–4.19
Tikhaya Sosna–Alekseevka
60
0.51/7.82
0.24/0.65
–0.67/–4.02
Bityug–Bobrov
73
0.73/11.43
2.13/4.28
–4.77/–6.73
Podgornaya–Kalach
61
0.56/9.49
0.04/5.37
0.17/–5.56
Panovka
51
0.7/9.2
10.19/20.26
–3.91/–3.52
Balashov
92
0.47/4.84
7.24/5.92
–6.16/–8.66
Povorino
72
0.84/12.48
4.26/9.58
–8.35/–9.69
Novokhopersk
61
0.85/14.54
Besplemyanovskii
76
0.77/11.39
2.22/5.84
–6.25/–7.73
54
0.67/9.02
0.18/15.9
–1.45/–5.28
Chutanovka
66
0.84/10.48
4.1/10.1
–7.18/–6.89
Borisoglebsk
66
0.86/15.68
3.87/11.94
–6.31/–6.06
Kikvidze
52
0.56/4.57
3.18/10.5
–2.12/–2.17
Bol’shoi Luk’yanovskii
37
0.57/6.49
0.6/2.11
–0.85/–2.94
Zmiev
58
0.56/7.41
0.54/2.87
–2.32/–8.01
Lisichansk
49
0.39/4.76
0.91/2.58
–2.38/–4.34
Belaya Kalitva
73
0.48/5.69
0.68/1.72
–2.62/–3.46
Razdorskaya Krasivaya Mecha–Efremov Sosna
Khoper
Karai–Podgornoe
6.4/10.26
–6.44/–7.21
Vorona
Buzuluk
Severskii Donets
WATER RESOURCES
Vol. 40
No. 6
2013
CURRENT CHANGES IN RIVER WATER REGIME
where Qmin s is the minimal monthly water discharge over summer–autumn period, m3/s; yn is water runoff depth during spring flood, mm; QX is the mean monthly discharge during the previous October, m3/s. Such calculations were carried out for some gages, resulting in relatively high correlation coefficients between the calculated and actual values. Thus, at the Borisoglebsk gage on the Vorona R., this correlation coefficient is 0.75. According to the obtained relation ships, higher spring flood runoff is associated with lower dryseason water discharge. This can be explained by the fact that the high and shorttime spring flood suggests lesser groundwater recharge than that in the case of lower, smooth, and multipeaked spring flood. Factor analysis for winter runoff yields acceptable results (with r values up to 0.75) in the con struction of dependences of mean winter discharges on the total liquid precipitation and mean tempera tures of the cold season. Such empirical–statistical approaches to forecasting seasonal runoff require fur ther improvement and refinement. It is worth mentioning that the absence of flow is typical of most small rivers in the region. Noflow periods were recorded in about 100 such rivers in the Don basin. The duration of such dry periods in small rivers of the basin is among the longest in ER, and the drainage areas average about 2000 km2, varying from 10 (Chibrik R., Rozhdestvenskoe V.) to 19000 km2 (Sal R., Martynovka V.). During the past 50 years, the total amount of intermittent rivers decreased by a fac tor of 2–3 [7]. At the same time, episodic drying of riv ers or noflow periods should be regarded as an extreme hydrological event. RUNOFF REGIME More than 20 gages on rivers with different drain age areas were chosen for studying the formation of spring runoff. The objects of studies were the runoff depth and volume during the spring flood, the dates of its beginning and end, the date of maximal water dis charge (and its modulus), the percentage of spring flood in the annual runoff, the abruptness factor of spring flood, which is equal to the ratio of the maximal modulus to the runoff depth during flood [8]. The spring flood runoff depth decreases southeast ward; its average for the basin over 1970–2008 is ~50 mm. The highest runoff depth forms in the Khoper Basin at Povorino gage (more than 60 mm), a lower depth forms in the Medveditsa Basin (30– 40 mm), and the lowest spring flood runoff (20– 30 mm) is typical of the basins of the rivers of Buzuluk, Ilovlya, and tributaries of the Lower Don. The spring flood depth decreases by 10–30% all over the basin, the decrease reaching its maximum in the upper reaches of the Don (upstream of Liski gage), were the runoff depth was maximal before. Statistical analysis of runoff depth series has shown a statistically signifi WATER RESOURCES
Vol. 40
No. 6
2013
Qd summer, m3/s 60
579 (а)
50 40 30 20 10 0
10
5
15
Qcalc, m3/s
20
25 30 35 Qd winter, m3/s
(b)
250 200 150 100 50 0
50
100
150
200 250 Qfact, m3/s
Fig. 3. Relationship between (left) mean winter and sum mer dryseason runoff in the Vorona R. at Borisoglebsk T. and (right) between actual dryseason runoff of the Don at Liski T. and its estimates by multiple regression equation.
cant decrease in the expectation at 60% of gages and a statistically significant increase in the variance, which, in combination, suggest a considerable degradation of spring flood on rivers as a phase of water regime under current climate conditions. The spring flood depth shows wide variations. The coefficient of variation in the basin of the Upper and Middle Don is 0.4–0.6, whereas that in the tributaries of the Lower Don (the Kalitva and Chir) is 0.8–0.9. Changes in spring runoff and degradation of spring flood in the basin can be clearly seen in the dynamics of maximal water discharges. From the early 1930s to the 2000s, the maximal runoff modulus decreased (L/(s km2) from 100 to 40 in the Upper Don (Zadonsk T.), from 140 to 40 in the Sosna R., and from 60 to 20 in the Vorona R. (Borisoglebsk T.). The aver age decrease in the maximum runoff modulus in the basin is 40–60%. Statistical analysis of series of maximal runoff moduli for 1970–2008 as compared with 1936–1969 showed a statistically significant descending trend and
580
DZHAMALOV et al. (а) 42°
44°
Para
40°
Uz a Vorona
Tsna
Voro ne
1.5 ug Bity
52°
Med
S
ec ha
Sa val a
Ok a
M
Sura
Ilovlya
Kr as iva ya
E
zh
W
Lesnoi Voronezh
va no Ra
46°
a sh Vy
N
54°
d Va
54°
ra izd Zh
38°
vedi tsa
36°
07
im Se
El
an
1.5
0.3
So sn a
a
50° ogra Volg
Chi r
46°
kii
Don e
48°
Ts
Sev ers
im lya nsk oe
Re s.
Aidar
Don ets
a
Darkul
ay sn
Kalitva
Oskol
Aidar
Seve rskii
a Kr
Kh ope r
s.
aya Kal itv
k
vly a
Che rn
zul u
Ilo
Oskol
skla Vor
Tamulaevk a
Ti kh ay a
Bu
d Re
Psel
ts
sk in rp Sa
0.7
ke La ie
Do n
Sal Ves e
rivers major river
46° k
0. 3
Kalaus
n ba Ku
l. L Bo a ab
a lay Be
Changes in minimal winter monthly runoff modulus, % <0 0–50 50–100 100–200 >200 lakes
Egorlyk
Eya
or ly
46°
lovs koe Res .
Eg
Minimal winter monthly runoff modulus, L/(s km2)
s
Tuzlov
Ur u p
Russia Ukraine seas
44° 36°
60 38°
40°
0
42°
60 km
44°
44°
Fig. 4. Minimal moduli of monthly (a) winter and (b) summer runoff in 1970–2008 and its changes relative to 1936–1969.
a considerable decrease in variance at almost all gages. Changes in the shape of spring flood cause appre ciable changes in the coefficient of flood abrupt
ness—a major calculated characteristic. The coeffi cient of abruptness decreases significantly at all gages, in many rivers, by a factor of 1.5–2. WATER RESOURCES
Vol. 40
No. 6
2013
CURRENT CHANGES IN RIVER WATER REGIME
581
42°
44°
52°
Med
Bity ug
Sa va la
0. 7
52°
1.5 Uza 0.7
Vorona
Vor one
Tsna
zh
Ok a
ec ha
Sura
Ilovlya
2. 5
S
nezh
a sh Zu
as iva ya M
vedit sa
5
Kr
54° 46°
a sh Vy
E
W
Lesnoi Voro
Ra no va
Para
40°
1.
Zh izd r
54°
38°
d Va
a
(b) 36° N
Se im
El an
So sn a
Bu zul uk
50°
0.3 grad
46°
Volgo
Darkul
Oskol kii
Kalitva
ya na as Kr
Aidar
Sev ers
er Ilo v
Aidar
50° 1 .5
Kh op
Res.
rnay a Ka litva
lya
Che
Tamulae vka
Ti kh ay a ol Osk
skla Vor
Se ver s
2.5
kii Do ne ts
Psel
Chir
Se ver ski i
48°
0 .7
rivers major river lakes
48° Sa rp in sk ie
Sal n Do
Ve sel ov
La ke s
sko eR es.
Egorlyk
Eya
0. 7
46°
Eg o
rly k
1.5
n ba Ku l. Bo ba La
aya Bel
Minimal summer monthly runoff modulus, L/(s m2) Changes in minimal summer monthly runoff modulus, % <0 1–30 30–60 60–120 >20
0.3
0.3 Tuzlov
46°
D on e ts
Kalaus
1.5
Tsi mly ans k oe
Re s .
Donets
p Uru
Russia Ukraine seas
44° 36°
0 38°
40°
Fig. 4. (Contd.) WATER RESOURCES
Vol. 40
No. 6
2013
42°
100 km 44°
44°
582
DZHAMALOV et al.
Interestingly, the spatial distribution of the mean coefficient of natural runoff regulation over 1970– 2007 is, as it were, of “counterzonal” character: its largest values (0.7–0.9) were recorded in the western and southwestern parts of the Don basin (Fig. 6).
Q, m3/s 120 100 80
1
2
60 40 20 0 1930
1950
1970
1990
2010 Years
Fig. 5. Changes in the minimal mean monthly water dis charges in the Khoper R. at Besplemyanovskii V. over (1) winter and (2) summer–autumn periods.
The identification of spring flood as a separate phase in runoff hydrographs has become a complex problem in recent years. The larger number of thaws leads to dispersion of the beginning and end of the highwater phase: the date of the beginning of spring flood wave shifted 9–12 days earlier in the western part of the region and about a week in its eastern part. A general tendency is a shift of dates of the end of flood by 5–10 days on the average. Overall, the changes in the dates of floods lead to a statistically significant increase in its duration: it increases by 10–20 days, depending on the size of the river and the position of the basin. Climate changes cause changes in the minimal and maximal runoff, the mean annual water discharge in rivers in the basin remaining nearly unchanged, result ing in withinyear runoff distribution and radical changes in the characteristic shape of hydrograph. According to B.D. Zaikov classification, before the 1970s, the rivers of the basin showed East European type of water regime with a distinct spring flood, accounting for more than 50% of the annual runoff, and with maximal discharges exceeding dryseason ones on the average by a factor of 10. The typical hydrographs of the 2000s look quite different. The higher, wavelike runoff in winter, resulting from the larger number of thaws, reduces the water storage of snow cover before the beginning of spring flood, whose hydrograph becomes a flat, gentle curve with 3–4 peaks, an order of magnitude lower than those in the first half of the XX century [1–4]. Such changes in the annual runoff distribution manifest themselves in the dynamics of the coefficient of natural runoff regulation. On the one hand, we have a decrease in the percentage of spring flood (above base runoff), and on the other hand, an increase in dryseason water runoff (base flow). Such double effect results in a statistically significant increase in the expectation and a statistically significant positive trend in the coefficient of natural regulation of runoff in all rivers in the basin.
CONCLUSIONS Integral regional estimates of water resources in the southern regions of ER are given along with the space and time generalization of water regime characteris tics of rivers, taking into account current hydrometeo rological data. Statistically significant changes were identified in the minimal and spring flood river runoff, the mean annual water discharges remaining nearly constant. A considerable and statistically reliable increase was established in the dryseason (groundwater) runoff— the natural groundwater resources, whose volume increased by 1.5–2 times in different regions. Analysis of longterm variations of the characteris tics of minimal monthly runoff showed almost ubiqui tous manifestation of increasing trends for the exam ined rivers. The increase in the minimal monthly run off moduli relative to the mean over 1936–1969 was 30–60% in the major portion of the region, reaching 100–120% in the lefthand tributaries of the Severskii Donets. The main cause of the changes in the water regime is an increase in the groundwater recharge of rivers because of the growing moistening of East European Plain. It is closely related with changes in atmospheric circulation, an increase in the number of thaws, and a decrease in the soil freezing depth, which contribute to the replenishment of subsoil water reserves in winter. The majority of rivers show a statistically reliable decrease in the runoff depth during spring flood by 30–40%. The decrease in the maximal runoff modulus averages 40–60%. At the same time, maximal water discharges decrease ubiquitously. The change in the shape of the spring flood causes a considerable decline in the abruptness coefficient (by a factor of 1.5–2). Changes in the characteristics of spring flood in rivers in the basin manifest themselves in changes in its dates and durations. Such changes are most significant in the western part of the region, where spring flood starts 9–12 days earlier. The changes in the water regime cause runoff redis tribution within a year and an increase in the coeffi cient of natural regulation by 1.5–2 times, thus chang ing the typical shape of hydrograph. Considering the current climate changes, the intense development of water resources, and the load on them, it is necessary to take measures to reduce the risks of extreme hydrological situations. The obtained estimates of water resources and run off regime, as well as the relationships and the series of maps will be of use in the development of measures for WATER RESOURCES
Vol. 40
No. 6
2013
CURRENT CHANGES IN RIVER WATER REGIME 40°
54° 44°
ra Pa
N
Do n Kr a
E
M
ec ha
Uz
Vorona
Voro nezh
S
46°
Ilovlya
siv ay a
oi Voron ezh Lesn
3
W
Sa va la
Ok a
42° d Va
54°
38°
ra
52°
a
Medv editsa
36° izd Zh
583
52°
Se im
an El
So sn a
Psel
Bu zul uk
Aidar
Se v ers kii
aya asn Kr
Don ets
50° es.
per
Chi r
Darkul
Oskol
50°
Kh o
rad R
Aidar
a Ka litva
Volgo g
Cher nay
Tamulaevk a
Ti kh ay a
ol Osk
skla Vor
Seve rskii
Don ets
48° ie sk in rp Sa
48°
s ke La
Tuzlov Ves elo v
rivers major rivers lakes Don basin
Egorlyk Tsi mly ans koe R
seas Eg
or
Coefficient of natural runoff regulation
an
l. Bo
0.5–0.7
ba La
0.7–0.8
p Uru
0.8–0.91
Countries Russia Ukraine
36°
Kalaus
b Ku
0.3–0.5
44°
46°
es.
lyk
46°
sko eR es.
0 38°
40°
42°
100 km 44°
Fig. 6. Distribution of mean coefficient of natural runoff regulation over 1970–2008. WATER RESOURCES
Vol. 40
No. 6
2013
44°
584
DZHAMALOV et al.
the use and protection of water resources in the south ern Russia. ACKNOWLEDGMENTS This study was supported by the Russian Founda tion for Basic Research, projects nos. 110500467, 130500113; NOTs, project no. 20121.112.000 1008–4763; and under the program of state RF Gov ernment support of researches in Russian higher edu cation institutions, project no. 11.G.34.31.0007. REFERENCES 1. Vodnye resursy Rossii i ikh ispol’zovanie (Water Resources of Russia and Their Use), Shiklomanov, I.A., Ed., St. Petersburg: GGI, 2008. 2. Georgievskii, V.Yu., Effect of anthropogenic climate changes on hydrological regime and water resources, in Izmeneniya klimata i ikh posledstviya (Climate Changes and Their Consequences), St. Petersburg: Nauka, 2002, pp. 152–164. 3. Dzhamalov, R.G., Frolova, N.L., Krichevets, G.N., et al., The formation of presentday resources of sur face and subsurface waters in European Russia, Water Resour., 2012, vol. 39, no. 6, pp. 623–639. 4. Dzhamalov, R.G., Frolova, N.L., Kireeva, M.B., and Safronova, T.I., Dynamics of groundwater runoff in Don Basin under the effect of climate changes, Nedropol’zovanie, XXI Vek, 2010, no. 4, pp. 78–81.
5. Dmitrieva, V.A., Geographic–hydrological assessment of water resources in a constituent territory of the Rus sian Federation under changing climate and economic activity, Extended Abstract of Doctoral (Geogr.) Disserta tion, Voronezh, 2012. 6. Doklad ob osobennostyakh klimata na territorii Rossi iskoi Federatsii za 2012 god (Report on Specific Fea tures of Climate in RF Territory in 2012), Moscow: Rosgidromet, 2012. 7. Kireeva, M.B. and Frolova, N.L., Noflow periods in rivers in Don Basin, Vestn.Mosk. Univ., Ser. 5: Geogr., 2010, no. 4, pp. 47–54. 8. Kireeva, M.B. and Frolova, N.L., Presentday features of spring flood in rivers in Don Basin, Vodnoe khozyaistvo Rossii: problemy, tekhnologii, upravlenie, 2013, no. 1, pp. 60–76. 9. Kislov, A.V., Evstigneev, V.M., Malkhazova, S.M., et al., Prognoz klimaticheskoi resursoobespechennosti VostochnoEvropeiskoi ravniny v usloviyakh potepleniya XXI veka (Forecast of Climatic Resource Availability in East European Plain under Warming in the XXI Cen tury), Moscow: MAKSPress, 2008. 10. Scheme of integrated use and protection of water bod ies in the Don Basin. http://www.donbvu.ru/ ne_4847728. 11. Dzhamalov, R.G., Frolova, N.L., Kireeva, M.B., and Safronova, T.I., Climateinduced changes in ground water runoff in Don Basin, Water Resour., 2010, vol. 37, no. 5, pp. 733–742. Translated by G. Krichevets
WATER RESOURCES
Vol. 40
No. 6
2013
