Irrigation Water Supply And Demand In Responese To Changing Environment And Agriculture Water Safty Evaluation

In recent decades, the changing environment which consists of climate change andhuman activities has imposed a significant impact on both global and regional water supplyand demand balance. Deterioration of climate change and increasing intensity of humanactivities made agricultural water safety issue stands out. Irrigation area serves as thefoundation of ensuring food security and promoting social development, so the importance ofsupply and demand balance of agricultural water and water safety become evident. Theresearch on agricultural water supply and demand and its security in the changingenvironment, can make a guidance and reference to deal with the risks of droughts and watershortage, promote reasonable agricultural structure, and contribute to modern water-savingand high-efficient agriculture. This paper studied agricultural water supply and demandsystem of typical northern irrigation area, analyzed temporal and spatial variables of thechanging environmental and its impacts. The agricultural irrigation water supply and demandsystem model was established on system dynamics, with a purpose to simulate the futureenvironmental changing scenarios and discuss and evaluate agricultural water safety inirrigation areas. The main contents and conclusions of this paper are as follows:(1) The paper took the Baojixia Irrigation area as the research background, analyzed thewater system of supply and demand in agricultural irrigation area, and found theenvironmental factors leading to the change of water supply and demand. Also, the temporaland spatial variation of the changing environmental factors was analyzed by means of Kendalltest, the linear trend estimates, residual mass curve, GIS technology, etc. It concluded that, inthe past three decades, temperature and evaporation increased significantly in the irrigationarea, while relative humidity, rainfall and wind speed decreased dramatically, which showsthat the climate tends to be warmer and drier; the spatial distribution showed that fromsouthwest to northeast in this area the climate tends to be warmer and drier. Thus, theagricultural acreage and proportion of food crops was declined significantly and cash cropssuch as fruit trees are increased rapidly. The main water source of irrigation area, the runoff ofWeihe River in Linjiacun section decreased significantly.(2) Based on the calculation of agricultural water demand, the dissertation analyzedchanging environmental factors and their impact on agricultural water demand. The referencecrop evapotranspiration increased significantly in the past30years, and was in gradualincrease spatially from southwest to northeast. Overall agricultural irrigation water demanddecreased, and the direct factor is the decrease in agricultural acreage and planting structureadjustment. Analysis result of gray correlation method indicated that: The sequence of humanactivities impacts on water demand is as follows: the planting area, planting structureirrigation water effective utilization coefficient. Rainfall is the most significant fact of climate change which influences water demand, and followed by sunshine duration, wind speed,average temperature, and relative humidity. By creating the influence formula ofenvironmental factors on agricultural water demand, the paper roughly estimate the impact offactors on agricultural water and the amount in the simulated scenarios. Through variationpoint divides and the changing environment sub-sequence, the author estimates hydrologicalfrequency eigenvalues of river runoff, in different changing environments. This methodprovides feasible measures to calculate water supply under changing environment.(3) By using the system dynamics theory and STELLA software，the agriculturalirrigation water supply and demand system model is built. Considering of the trends ofchanging environments factors, a group of future scenarios was set to simulate the response ofirrigation agriculture water supply and demand model to climate change and human activities.Results of the Model experiments show that: Agricultural water demand in irrigation area issignificantly influenced by future climate change. In average year (P=50%),agricultural waterdemand rises10.06%in recent planning year than present year, and rise9.31%in long termplanning year than the recent planning year. In moderately dry year (P=70%),agriculturalwater demand rises7.78%in recent planning year than present year, and rise5.78%in longterm planning year than the recent planning year. By strengthening irrigation water-savingplanting, the cultivation area can be reduced by18.71%.,thus lead to an decrease of24%,23%, and22%of net agricultural water demand in wet year, normal year and dry yearrespectively.(4)The thesis analyzed factors concerning water safety in agricultural area underchanging environment. Based on Analytic Hierarchy Process and supply and demand balanceindex, established Comprehensive Evaluation Model of agricultural water safety. Theevaluation concluded that the Baojixia Irrigation agricultural water is slight risk in wet yearand average year, moderate risk in dry year. And the overall evaluation of irrigation area isslight risk.Finally, in light of the changing environment and agricultural water safety, severalmeans were suggested to ensure agricultural irrigation water safety.