Improving water saving measures is the necessary way to protect the ecological base flow of rivers in water shortage areas of Northwest China

Abstract Low efficiency of water use in agricultural irrigation is the main obstacle preventing river ecological base flow protection in water shortage areas in Northwest China. By constructing a quantitative calculation model, the important contribution agricultural irrigation water-saving measures have on river ecological base flow protection are quantitatively analyzed in this study. Firstly, we determine water demand of the river ecological base flow combined with the river protection goal, determining water shortage in non-flood seasons combined with residual water in rivers after irrigation diversion. Secondly, we quantitatively determine water saving by combining water saving measures. Finally, we use water balance analysis to quantitatively calculate the protection degree and the protection rate of the river ecological base flow. Calculation results indicate that river ecological base flow from October to May of the next year is [5.66, 7.42 m3/s] and is greater than or equal to 21.69 m3/s from June to September. Total water saving after improving water saving measures are 66.55, 133.11 and 205.66 million m3 under three proposed scenarios; protection degree and protection rate after improving water saving measures in non-flood seasons under the three scenarios are 59.38%, 93.66% and 100%, and 45.92%, 74.02% and 100%, respectively, which gradually reached the target protection rate of 90% for river ecological base flow required by administrative departments. Comparison of advantages, disadvantages and costs of the three main protection modes indicated that improving water saving measures are the most reasonable protection measure to protect the ecological base flow of rivers. By using a quantitative study, a basis for reasonable safeguard measures of the ecological base flow of rivers in water shortage areas of Northwest China are presented.