| With continuous population growth and economic and social development,human demand for water resources is growing rapidly.Due to uneven spatial and temporal distribution of water resources and various unreasonable ways of water resources development and utilization,the contradiction between water supply and demand becomes serious.Optimal allocation of water resources is the most effective' way to solve this problem.The frequency and intensity of extreme hydrological events are increasing under global climate change,and the uneven spatial and temporal distribution of water resources is further aggravated.The water resources allocation model based on historical data series is no longer applicable to future water resources planning.Therefore,it is of great theoretical and practical significance to study optimal allocation of water resources based on hydrological cycle simulation under climate change scenarios.In this study,the middle and lower reaches of the Hanjiang River basin were selected as case study,and the main contents and conclusions were summarized as follows:(1)Based on the daily bias correction model(DBC),the outputs of 19 GCMs were downscaled to project precipitation and temperature changes in the Hanjiang River basin.Results indicate that the DBC model performs reasonably well in simulating the amount and frequency of daily precipitation as well as the daily maximum and minimum temperature.Compared with the base period,annual precipitation,maximum and minimum temperature shows a general increase under RCP4.5 and RCP8.5 scenarios.With the increase of radiative forcing,the growth rate under RCP8.5 is greater than RCP4:5.(2)The GCMs downscaling results were used as inputs of the VIC distributed hydrological model,and then projected changes of future runoff in the Hanjiang River basin were simulated and predicted.Results indicate that the annual runoff has an increasing trend under two scenarios compared with the base period,while the growth rate under RCP8.5 is greater than RCP4.5 except for Huangzhuang station.Moreover,an overall increasing trend is detected for both the amounts of local water resources and the Danjiangkou reservoir inflows,particularly in the flood season,while the trend is not significant in the dry season.(3)According to the calibration and revision of the water use index and quota for the base year 2010,the index analysis method was employed to predict water demand of each sector in the middle and lower reaches of the Hanjiang River basin.Results indicate that the total water demand increases with the increase of water demand frequency and planning levels.The urban and rural domestic water demand increases slightly,while the industrial water demand increases greatly.At the same precipitation frequency,the agricultural water demand shows a decreasing trend from year 2020 to year 2040.In all sub-areas of tertiary water resource zones coupling county-level administrative district,the total water demand of Xiangyang region is the largest.(4)According to sub-areas of forth-level water resource zones coupling municipal administrative district,water resources allocation model was developed based on MIKE BASIN.Considering the operation and dispatching of 17 large and medium-sized reservoirs and the water transfer projects,optimal allocation of water resources under climate change was analyzed.Results show that the total water deficit is gradually increasing in both the historical and future periods.At the same planning year,the total water deficit slowly increases along with less water resources.Under the same water demand scheme,the water deficit in future is slightly smaller than that in the historical period.In all water sectors,there are mostly no water shortages for the urban and rural domestic water demand,while there are different degrees of water shortage in urban industrial,agricultural irrigation and ecological water demand.Moreover,there is no water shortage in all water supply areas along the Hanjiang River mainstream. |
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