JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 114, D07102, doi:10.1029/2008JD010537, 2009 Click Here for Full Article Variation of hydrological regime with permafrost coverage over Lena Basin in Siberia Baisheng Ye,1 Daqing Yang,2 Zhongliang Zhang,3 and Douglas L. Kane2 Received 3 June 2008; revised 18 November 2008; accepted 4 February 2009; published 2 April 2009. [1] We use monthly discharge and permafrost data to examine the relationship between discharge characteristics and basin permafrost coverage for the nested subbasins of the Lena River in Siberia. There are similarity and variation in streamflow regimes over the basin. The ratios of monthly maximum/minimum flows directly reflect discharge regimes. The ratios increase with drainage area from the headwaters to downstream within the Lena basin. This pattern is different from the nonpermafrost watersheds, and it clearly reflects permafrost effect on regional hydrological regime. There is a significant positive relationship between the ratio and basin permafrost coverage. This relationship indicates that permafrost condition does not significantly affect streamflow regime over the low permafrost (less than 40%) regions, and it strongly affects discharge regime for regions with high permafrost (greater than 60%). Temperature and precipitation have similar patterns among the subbasins. Basin precipitation has little association with permafrost conditions and an indirect relation with river flow regimes. There exists a good relation between the freezing index and permafrost extent over the basin, indicating that cold climate leads to high coverage of permafrost. This relation relates basin thermal condition with permafrost distribution. The combination of the relations between temperature versus permafrost extent, and permafrost extent versus flow ratio links temperature, permafrost, and flow regime over the Lena basin. Over the Aldan subbasin, the maximum/minimum discharge ratios significantly decrease during 1942–1998 due to increase in base flow; this change is consistent in general with permafrost degradation over eastern Siberia. Citation: Ye, B., D. Yang, Z. Zhang, and D. L. Kane (2009), Variation of hydrological regime with permafrost coverage over Lena Basin in Siberia, J. Geophys. Res., 114, D07102, doi:10.1029/2008JD010537. 1. Introduction permafrost changes, and human impacts [Peterson et al., 2002; Yang et al., 2002; Ye et al., 2003; McClelland et [2] River runoff is the primary freshwater source to the al., 2004]. Arctic Ocean. Fresh water discharge from the northern- [3] In the cold regions, hydrological regime is closely flowing rivers plays an important role in regulating the related with permafrost conditions, such as permafrost thermohaline circulation of the world’s oceans [Aagaard extent and thermal characteristics. Ice-rich permafrost has and Carmack, 1989]. Both the amount and the timing of a very low hydraulic conductivity and commonly acts as a freshwater inflow to the ocean systems are important to barrier to deeper groundwater recharge or as a confining ocean circulation, salinity, and sea ice dynamics [Aagaard layer to deeper aquifers. Because it is a barrier to recharge, and Carmack, 1989; Macdonald, 2000]. Recent studies permafrost increases the surface runoff and decreases sub- report significant changes in arctic hydrologic system, surface flow. Permafrost extent over a region plays a key particularly cold season and annual discharge increases over role in the distribution of surface-subsurface interaction large Siberian watersheds. These changes indicate hydro- [Lemieux et al., 2008; Carey and Woo, 2001; Woo et al., logic regime shifts due to large-scale climate variations, 2008]. Permafrost and nonpermafrost rivers have very different hydrologic regimes. Relative to nonpermafrost basins, permafrost watersheds have higher peak flow and 1States Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of lower base flow [Woo, 1986; Kane, 1997]. In the permafrost Sciences, Lanzhou, China. regions, watersheds with higher permafrost coverage have 2Water and Environment Research Center, Civil and Environmental lower subsurface storage capacity and thus a lower winter Engineering Department, University of Alaska Fairbanks, Fairbanks, base flow and a higher summer peak flow [Woo, 1986; Alaska, USA. 3Department of Resources and Environment, Lanzhou University, Kane, 1997; Yang et al., 2003]. Lanzhou, China. [4] It is difficult to accurately determine changes in permafrost conditions. Our understanding of permafrost Copyright 2009 by the American Geophysical Union. change and its effect on hydrological regime is incomplete. 0148-0227/09/2008JD010537$09.00 D07102 1of12 D07102 YE ET AL.: STREAMFLOW REGIME VERSUS PERMAFROST COVERAGE D07102 Figure 1. The Lena River watershed and hydrological stations (A through K) used in this study. Also shown are the reservoir location on the Vilui River and the permafrost distribution [Brown et al., 1997, 2001] over the Lena basin. For instance, there are uncertainties regarding the impact of 15% of the total freshwater flow into the Arctic Ocean ground ice melt and its contribution to annual flow changes [Yang et al., 2002; Ye et al., 2003]. Relative to other large over large Siberian rivers [McClelland et al., 2004; Zhang et rivers, the Lena basin has less human activities and much al., 2005a]. Permafrost condition and streamflow character- less economic development [Dynesius and Nilsson, 1994]. istics vary within large watersheds in Siberia. Examination There is only one large reservoir in the Vilui subbasin. A and comparison of hydrological regimes between subbasins large dam (storage capacity 35.9 km3) and a power plant with various permafrost conditions can improve our under- were completed in 1967 near the Chernyshevskyi standing of impact of permafrost changes on cold region (112°150W, 62°450N). This reservoir is used primarily for hydrology. This paper examines the relationship between electric power generation: holding water in spring and hydrological regime and permafrost coverage over nested summer seasons to reduce snowmelt and rainfall floods subbasins within the Lena River in Siberia. It analyzes and releasing water to meet the higher demand for power in monthly discharge data, with a focus on the ratio of the winter [Ye et al., 2003]. Various type of permafrost exists maximum to minimum discharge (Qmax/Qmin) and its in the Lena basin, including sporadic, or isolated permafrost relation with permafrost condition, because this ratio in the source regions, and discontinuous and continuous reflects the hydrological regime. The objective of this study permafrost in downstream regions (Figure 1) [Brown et al., is to quantify the impact of permafrost on streamflow 1997]. Approximately 78–93% of the Lena basin is under- regime and change, and to specifically define a relationship lain by permafrost [Zhang et al., 1999; McClelland et al., between basin permafrost extent and streamflow conditions 2004]. over the Lena watershed. We also examine relationship [6] Since the late 1930s hydrological observations in the between basin air temperature and precipitation and their Siberian regions, such as discharge, stream water tempera- effect on permafrost extent and basin streamflow regimes. ture, river ice thickness, dates of river freezeup and breakup, The result of this study will shed light on our knowledge of have been carried out systematically by the Russian Hydro- cold region hydrology and its change due to climate impact meteorological Services and the observational records and human influence. were quality-controlled and archived by the same agency [Shiklomanov et al., 2000]. The discharge data are now 2. Basin Description, Data Sets, and Method available from the R-ArcticNet (v4.0), a database of Pan- of Analysis Arctic River Discharge during 1936–2000 [Lammers et al., 2001]. In this analysis, long-term monthly discharge records [5] The Lena River originates from the Baikal Mountains collected at 9 stations (A–H and K) along the main stem in the south central Siberian Plateau and flows northeast and and 2 tributary stations (I and J) were used (Figure 1). north, entering into the Arctic Ocean via the Laptev Sea Relevant information of these stations is given in Table 1. 2 (Figure 1). Its drainage area is about 2,430,000 km , mainly [7] Permafrost data and information were obtained from covered by forest and underlain by permafrost. The Lena the database of the digital permafrost map compiled by River contributes 524 km3 of freshwater per year, or about International Permafrost Association (IPA) [Brown et al., 2of12 D07102 YE ET AL.: STREAMFLOW REGIME VERSUS PERMAFROST COVERAGE D07102 Table 1. List of Hydrologic Stations Used in This Studya Station Code Latitude Longitude Drainage Area Annual Runoff (see Figure 1) Station Name/Location (°N) (°E) Data Period (Â1000 km2) %km3 mm % A Kachug 53.97 105.88 1936 1990 17 0.7 2.9 164.0 0.5 B Zhigalovo/Upper Lena 54.82 105.13 1969 1977 30 1.3 3.8 124.6 0.7 C Gruznovka/Upper Lena 55.13 105.23 1912 1990 42 1.7 6.2 148.0 1.2 D Ust’-Kut/Upper Lena 56.77 105.65 1936 1986 71 2.9 10.1 141.9 1.9 E Zmeinovo/Upper Lena 57.78 108.32 1936 1990 140 5.8 35.4 253.1 6.7 F Krestovskoe/Upper Lena 59.73 113.17 1936 1999 440 18.1 131.3 298.5 24.8 G Solyanka/Upper Lena 60.48 120.7 1933 1999 770 31.7 213.5 277.2 40.4 H Tabaga/Upper Lena 61.83 129.6 1936 1999 897 36.9 221.0 246.4 41.8 I Verkhoyanskiy Perevoz/ 63.32 132.02 1942 1999 696 28.6 166.0 238.5 31.4 Aldan subbasin outlet J Vilyuy/Vilui valley outlet 63.95 124.83 1936 1998 452 18.6 46.7 103.3 8.8 K Lena At Kusur 70.68 127.39 1934 2000 2430 100.0 528.6 217.5 100.0 aStations A–H are listed from upstream to downstream. 1997, 2001]. The shapefiles were derived from the original itation and temperature and their relationships with basin 1:10,000,000 printed map.