Study On Changes In Water Resources And Drought Vulnerability Assessment In The Guanzhong Plain

Under climate change,amounts and structure of water resources have changed,and many regions trend to drought.Because of the severer drought and enhancement of disaster reduction,it requires a paradigm shift from crisis management to risk management.As a basis and key of risk management,it is necessary to develop a scientific and feasible assessment for drought vulnerability that helps to identify where vulnerabilities exist,thus we can develop and implement mitigation and adaptation measures to lessen the risk.Northwest China with fragile ecology is sensitive to climate change.Taking the Guanzhong Plain as a case study,this paper studies the changes of water resources and drought vulnerability assessment.The main content and conclusions are as follows:(1)The CRU TS and GPCC datasets are used to supplement the limited data from meteorology stations.The linear regression and some popular methods in recent years,such as the trend-free pre-whitening Mann–Kendall test(TFPW–MK),quantile perturbation method and partial trend method(PTM),are employed to analyse changes in precipitation and streamflow.Specifically,we study changes in total precipitation,oscillatory behavior of precipitation extremes,precipitation changes in different magnitudes,changes in precipitation structure,changes in streamflow of the Weihe and Jinghe River,oscillatory behavior of streamflow extremes,streamflow changes in different magnitudes,streamflow changes in the four seasons,spatial characteristics of groundwater and dynamic variations of groundwater table.Critical findings are as follows:In nearly half a century,precipitation is prevailing decline in the Guanzhong Plain.Precipitation of low values has a larger decrease than other values,which implies an accelerating drought trend.Rainy days show a prevailing positive trend,while precipitation intensity shows a negative trend.This indicates a trend of centralized distribution in precipitation that increases probabilities of drought.Significant anomalies in precipitation extremes exhibit nearly a 35-year cycle.The positive anomaly shows a closely related to floods.Changes in streamflow are consistent with precipitation.In nearly half a century,streamflow of the Weihe and Jinghe River is significantly downward,mainly in moderate–high flows.From the middle to the lower reaches,the decreasing trend is weakened because of weakened trend in low–moderate flows and absent trend in autumn and winter.The Jinghe River is the largest tributary of the Weihe River,but their streamflow trends in four seasons are dramatically different.This may be an important reason for the spatial variations in streamflow trend of the Weihe River.(2)Without a quantization of changes,PTM is hard to apply for a large mass of data and compare trends between series.This study derives a PTM index to represent changes,and proposes a bootstrap procedure to test statistical significance.The results of PTM are consistent with the linear regression and the TFPW–MK.This demonstrates that statistically significant changes identified by a relative variation in previous studies will increase the probability of type I error.The improved PTM improves test efficiency,accuracy and applicability.Because PTM can analyse overall change in mean values and changes in different magnitudes,it deserves promotion in meteorological and hydrological fields.(3)Study of drought vulnerability started later.This study selects the overlay and index method for drought vulnerability assessment,which is the most proven technique in hydrogeology.To avoid synergy and antagonism between indices,eight indices are selected from a dozen impact factors by the high correlation filter and low variance filter.To avoid defects in subjective and objective weighting methods,the weighting scheme combines the analytic hierarchy process and the entropy method.Drought vulnerability map is produced on a GIS platform based on high resolution raster data of physical geography and social economy that are obtained from modern techniques,such as remote sensing,interpolation and computer simulations.The result shows a low sensitivity to remove an index map indicating a reliable model with a stable result.As a relative concept of vulnerability,low vulnerability areas still suffer from scarcity of irrigation water.Actually,water scarcity has posed a great threat to the Guanzhong Plain.This study proposes that drought vulnerability should be dynamic because of significant changes in water resources.The analysis reveals changes in precipitation increase overall drought vulnerability,and the effect is marked in the western areas of the plain.Drought has a trend of long duration and severe impacts.Changes in streamflow increase vulnerability in Baojixia irrigation district,but decrease hiemal vulnerability in Jinghuiqu irrigation district.