Analysis Of Runoff And Hydrological Drought In Guanting Basin Based On Different Scenarios

According to the Fifth Assessment Report, climate was significantly changed in the past few years, almost every part of the world suffered global warming. Under the combined influence of human activity and climate change, water shortages and extreme hydrologic events frequently occur. As a crucial part of water cycle, the variations of runoff directly influenced exploitation and utilization of water resources, affect the stability of ecosystem as well as the social security. By simulating the runoff basin, we can understand more about the surface water resources status. This will provides some references for reasonable distribution of water resources, plays a vital role in people’s production and life, and also a key to environment and social stability.This paper took the Guanting basin as the studied area, HBV and SWIM hydrological model were applied to simulated the hydrological process of the basin, with the support of GIS. Based on the data of daily data simulated by a high-resolution (0.5°×0.5°) regional climate model CCLM (COSMO model in Climate Mode), the average hydrology state of Guanting basin from2014to2040under SRES-A1B scenario, SRES-B1scenario and RCP4.5scenario was analyzed. Also the runoff of the basin in the wet period and dry period were analyzed. Then use various distribution functions to fit the largest ID runoff series in order to calculate the flood frequency changes in the future. At last, drought and flood are analyzed based on the standardized drought index. The results are as follows:(1) The annual temperature in the Guanting basin shows a significant upward trend at a rate of about0.29degree per decade. More significant upward trend can be detected in winter. The precipitation shows a downward trend, as well as the runoff in Guanting basin, in addition, runoff catastrophe appeared in1984-1985.(2) Taking1971-1974as the calibration period,1975-1978as the validation period, HBV model and SWIM model are established. The results show that:HBV hydrological model is better than than SWIM model in simulating the runoff of Guanting basin, the decisive coefficient between simulated value and measured value in calibration and validation periods are0.68and0.70. HBV model has better applicability in Guanting basin, while human activities have an important impact on the hydrology and water resources to this basin.(3) Use the grid data output from CCLM (including three kinds of scenario, SRES-A1B scenario, SRES-B1scenario and RCP4.5scenario) to drive HBV model, daily runoff data is been simulated. The results show:In2014-2040, in yearly and monthly scale, precipitation and runoff decreased than the reference period (1971-2000). With temperature rising and summer rainfall decreasesing in the future, runoff in the wet period may reduce, but runoff in the dry season under these three scenario shows different results, that is to say, exist a big uncertainty.(4) Use various distribution functions to fit the largest1D runoff series to determin2best fitted distribution functions to calculate the flood frequency changes in the future. The distribution functions have been choosed based on the goodness of fit. By comparing these3set of data, we can see that:the flood frequency increased under the RCP4.5scenario and SRES-B1scenario, while flood frequency reduced under SRES-A1B scenario, which reflect the uncertainty in analysing future flood frequency in different scenarios. (5) Based on the runoff data from different climate scenarios’ simulation, using SDI has been used to analysis hydrological drought and flood in the future, the results show that there is a significant difference among different scenarios. Under the scenario of RCP4.5,2016-2017,2023-2025and2037-2039will be possible drought years in the future, while2020-2022,2026-2027and2033-2035will be possible flood years in the future. Under the scenario of SRES-A1B, the mainly dry period are2023-2025,2033-2034and2037-2039, the mainly wet period are2016,2018-2019,2023-2025and2040. Additionly, under the scenario of B1, the alternation of drought and flood frequency shows a significant difference with the former two scenarios, it can mainly be divided into3stages,2014-2023, dry period and wet period coexist,2024-2031, almost dry period and2032-2040, almost wet period.