Change Of Water Reserves In Recent Ten Years From GRACE And GLDAS In Dongting Lake Basin

Monitoring of river basin water reserves is important for studies of water resources variation and water balance.GRACE satellite provides a new measure for the research of variation of water reserves, GLDAS hydrological model data is often applied to estimate variation of water reserves.we estimate the terrestrial water storage change in the Dongting Lake basin using GRACE and GLDAS datas from 2003 to 2012,and contrasts the two results;The Dongting Lake basin is divided into the upper,middle and downstream,comparison of the three river basin on monthly and interannual variation;GRACE related impact factors are analyzed;Considered extreme change of water reserver.The result shows that:(1) GRACE satellite data estimate that water storage of Dongting Lake basin decreased progressively between 32.3mm and 150mm with a ladder-like shape from northeast to southwest on the space. GLDAS hydrological model estimate that water storage decreased from east to west with a range of variation between -60mm and 71.3mm.(2) GRACE water storage variation of Dongting Lake basin is between-135.76mm and 143.03mm on the time, the whole variation tendency rising year after year with a 0.5mm increase per month. GRACE water storage variation at all seasons is on the increase progressively in recent ten years, among all seasons, autumn increased 26.07 mm·a-1 with maximum increasing range. GLDAS water storage variation at all seasons is also on the increase, but its increasing range is smaller than GRACE data, and autumn increased 8.6 mm·a-1 with maximum increasing range.(3) The data of water storage variation of Dongting Lake basin obtained from GRACE and GLDAS presents differences on the space, GRACE and GLDAS data have a good consistency on time change process, at the same time, both show significant seasonal change. But the terrestrial water storage variation obtained from GRACE is greater than GLDAS, and shows one to two months hysteresis compare to GLDAS. Water storage variation of Dongting Lake basin based on GRACE and GLDAS has a good correlation, and the correlation coefficient is 0.67.(4) Water storage of GRECE and GLDAS presents a consistent variation monthly in the upper, middle and downstream of Dongting Lake basin, and water storage of both has the biggest change in the downstream, the second biggest change in the middle stream and the minimum change in the upper stream. Annual average water storage of GRACE and GLDAS presents a progressive increasing trend in the upper, middle, downstream and the whole basin. The increasing range of GRACE water storage is 3.75mm·a-1 ,6.24mm·a-1 ,8.86mm·a-1 and 6.28mm·a-1 in the upper, middle, downstream and the whole basin, and the corresponding increasing range of GLDAS water storage is 1.23mm· a-1,0.11mm·a-1,0.29mm·a-1 and 0.47mm·a-1, with a relative small increasing range compare to GRACE.(5) Rainfall is the main factor that affects terrestrial water storage variation. GRACE water storage and precipitation anomaly show a similar change process, the peak appeared caused by GRACE water storage variation is a month or so hysteresis compare to precipitation anomaly. GRACE date and precipitation anomaly show a moderate correlation coefficient of 0.51. The type of terrain and landform is another important factor that affects water storage of Dongting Lake basin. In addition, water come from Yangtze River has some influence on water storage of Dongting Lake basin.(6) GRACE water storage variation, GLDAS water storage variation and precipitation anomaly present a positive correlation relationship on the order of magnitude in 2004 and 2012. Water storage variation trend of GRACE and GLDAS show a good consistency in 2004 and 2012, and the correlation coefficient between the two is 0.75 and 0.68 respectively, but GRACE and precipitation anomaly present a relative low correlation.