Climate change effects on irrigation demands and minimum stream discharge: impact of bias-correction method

摘要

Climate changes are expected to result in a warmer global climate, withincreased inter-annual variability. In this study, the possible impacts ofthese climate changes on irrigation and low stream flow are investigatedusing a distributed hydrological model of a sandy catchment in westernDenmark. The IPCC climate scenario A1B was chosen as the basis for thestudy, and meteorological forcings (precipitation, referenceevapotranspiration and temperature) derived from the ECHAM5-RACMO regionalclimate model for the period 2071–2100 was applied to the model. Two biascorrection methods, delta change and Distribution-Based Scaling, were usedto evaluate the importance of the bias correction method. Using the annualirrigation amounts, the 5-percentile stream flow, the median minimum streamflow and the mean stream flow as indicators, the irrigation and the streamflow predicted using the two methods were compared. The study found thatirrigation is significantly underestimated when using the delta changemethod, due to the inability of this method to account for changes ininter-annual variability of precipitation and reference ET and the resultingeffects on irrigation demands. However, this underestimation of irrigationdid not result in a significantly higher summer stream flow, because thesummer stream flow in the studied catchment is controlled by the winter andspring recharge, rather than the summer precipitation. Additionally, futureincreases in CO₂ are found to have a significant effect on bothirrigation and low flow, due to reduced transpiration from plants.