基于生态需水保障的农业用水安全评价——以山东省引黄灌区为例

Evaluation of agricultural water-use security with ecological water demand as a priority: A case study of the Yellow River estuary in Shandong Province

保障农业用水安全和生态安全是流域水资源管理的重点,针对黄河口和山东引黄灌区的用水矛盾,采用阈值分析与地统计学方法,考虑作物蒸散发和有效降雨计算山东省引黄灌区灌溉需水量,在优先保障黄河口不同等级生态需水条件下分析灌区(划分为不同调控区)可用水量的响应特征,以地理信息系统(GIS)为平台计算具有时空差异的山东省引黄灌区农业用水安全压力指数,进而评价多时空尺度下的山东省引黄灌区农业用水安全。结果表明,在平水年,保障适宜等级的生态需水后大概有33%的年份农业用水安全存在压力,保障最低等级的生态需水约有27%的农业用水面临短缺,但是大部分情况下农业用水安全压力指数都在30%之下,然而保障最高等级生态需水后,有50%以上的年份存在农业用水安全压力,这种压力无论是从出现频次还是在指数强度上都有明显增加。在空间尺度上,以打渔张、刘春家、麻湾和簸箕李等灌区为代表的调控区2、11、13、14和17的农业用水压力显著,代表年内保障最低等级的生态需水后调控区的农业用水安全压力指数超过了20%,保障适宜等级的生态需水后,大部分调控区的农业用水安全压力指数超过了20%,调控区2和13的压力指数超过了30%,保障最高等级的生态需水后大部分调控区的农业用水安全压力指数超过了60%。在引黄水量调配过程中,应该按照水文年的不同保障合理的生态水量,同时充分考虑水文气象因子的空间差异性,在不同调控区细化分配方案,平水年份保障适宜等级生态需水后农业用水短缺由55.28降低到18.25亿m3。该评价方法反映了优先保障生态需水后灌区农业水资源保障情况,并能有效降低农业和生态用水之间的矛盾,为管理部门进行"精细配水"提供依据。

To address the conflicts of agricultural and ecological water use between the Shandong irrigation district and the Yellow River estuary, a method to evaluate the agricultural water-use security with the priority to meet ecological water demand is developed. A threshold analysis that takes into consideration evapotranspiration and effective rainfall is used to calculate irrigation water requirement. Then, a geo-statistical method is introduced to calculate irrigation water use for different regulatory regions with the priority to maintain different levels of environmental flows. Finally, a water-use security pressure index is introduced based on the geographic information system(GIS) platform, which is used to evaluate the spatial and temporal variations of water-use safety in the Shandong irrigation area. The results show that the maintenance of average and low levels of environmental flows could pose a pressure on agricultural water-use security for 33% and 27% of the average hydrological years, respectively. The corresponding pressure index is below 30% in most of the cases. The maintenance of a high level of environmental flows could pose a pressure on agricultural water-use security for 50% of the average hydrological years, with increases in the frequency and intensity of the pressure. In terms of spatial variations, the regulatory regions 2, 11, 13, 14 and 17(i.e., Dayuzhang, Liuchunjia, Mawan and Bojili) are experiencing more stress than the other regulatory regions. When meeting the demand of low-level environmental flows, the pressure indexes are over 20% in these regulatory regions. With the average level of environmental flow demand, the pressure indexes are over 20% in most regulatory regions and over 30% in regulatory regions 2 and 13. When the environmental flow demand increases to the high level, the pressure indexes are over 60% in most regulatory regions. In water resources management and planning, the allocation target of environmental flows for the Yellow River estuary should be carefully adjusted according to the changing hydrological conditions and the spatially-varied meteorological factors. An improved distributed allocation plan could reduce the water shortage from 5.53 to 1.83 billion m3 while meeting the average demand of environmental flows in average hydrological years. The evaluation method developed in this study can reflect the spatial and temporal variations of agricultural water-use security when ecological water demand is satisfied in priority. It can effectively mitigate the conflicts between agricultural and ecological water demands and provide a decision-making basis for water resources management.