Study on ecological water requirement for natural vegetation in Minqin County of Gansu Province | 甘肃省民勤县天然植被生态需水研究

Chinese. 研究干旱地区天然植被的生态需水量，为区域生态用水与经济用水的合理配置提供参考。针对西北干旱地区水资源短缺、降雨量少、植被退化、盖度降低等现状，以甘肃省民勤县为例,采用联合国粮农组织(FAO)提出的干旱区受破坏非完全覆盖的天然植被生态需水计算方法，计算植被生态需水定额，扣除有效降雨后得到生态缺水定额，再结合遥感解译的不同类型植被的生态植被面积，获得植被生态需水量和生态缺水量。民勤县植被适宜和最小的生态需水量在枯水年分别为7 652.0万和4 045.3万m3，平水年分别为7 554.9万和3 994.0 万m3，丰水年分别为6 546.3万和3 460.8万m3。植被适宜和最小的生态缺水量在枯水年分别为6 040.3万和2 433.7万m3，平水年分别为5 714.6万和2 153.8 万m3，丰水年分别为4 220.4万和1 331.4万m3。利用FAO提出的生态需水计算方法可以得到植被生长期各月生态需水量，计算结果与利用热脉冲法所得结果差异较小，说明该方法计算结果可靠，可以推广应用于其他干旱区。

English. The purpose of studying natural vegetation ecological water (EWR) is to provide reference for rational allocation of water between regional ecological and economic water usage in arid area. Considering the characters of the water shortage, little precipitation, degenerating vegetation and low coverage in northwest arid area of China, a new method of EWR for non-pristine、non-full coverage natural vegetation was introduced, which was proposed by FAO. The method was used to calculate the quota of EWR for vegetation. And the quota of water shortage for vegetation was obtained after deducting the effective precipitation. Combining with the different types of vegetation area interpreted from remote sensing, the volumes of EWR and water shortage for vegetation were obtained. Minqin County of Gansu Province was taken as an example in this study. The optimal EWR and the minimum EWR for vegetation in Minqin County in dry year was 76 520 000 and 40 453 000 m3 respectively, in average year 75 549 000 and 39 940 000 m3 respectively, in wet year 65 463 000 and 34 608 000 m3 respectively. The water shortage of optimal EWR and the minimum EWR for vegetation in dry year was 60 403 000 and 24 337 000 m3 respectively, in average year 57 146 000 and 21 538 000 m3 respectively, in wet year 42 204 000 and 13 314 000 m3 respectively. Monthly EWR can be obtained by the calculating method of EWR, which was proposed by FAO. Comparing the results with measured results by Heat pulse sap flow sensors, the difference is smaller. So the method is reliable and can be extended to other arid areas.