中文摘要：

以宁夏惠农灌域某个300hm~2的典型灌排单元为例,利用修改后的干旱区绿洲散耗型水文模型模拟水分收支,并计算两个灌溉用水效率指标（腾发量占净入流量比例和出流量占净入流量比例）随尺度变化规律,结果表明：1研究区以旱作为主,加之降雨较少,地表排水占土壤和地表水支出量的6.6%,重复利用水量占净入流量比例为9.7%;2腾发量占净入流量比例随尺度增大而增大,出流量占净入流量比例随着尺度增大而减小,种植结构的空间差异（水稻面积增加）对该尺度效应有负面影响,原因是水稻排水量相对较大使得用水效率降低;3由于回归水重复利用量相对偏少,用水效率随尺度提升效果有限,从单个地块提升到4个地块,腾发量占净入流量比例提升6.4%。

英文摘要：

Water budget was simulated in this study employing the modified runoff-evaporation hydrological model for the arid zone . Further more ,two kinds of irrigation water use efficiency indices （evaportranspiration fraction to the net inflow ,FRi for short ,and outflow fraction to the net inflow ,FRoi for short） across scales were calculated and analyzed ,taking a typical agri-hydrological unit （300ha） in Huinong Irrigation Scheme ,Ningxia Province as an example .The results indicated ：① because of less precipitation as well as dry crop dominantly cultivated ,runoff merely accounted for 6 .6% of the total amount of the soil consumption and the out‐flow ,the reuse of the return flow occupied for 9 .7% of the net inflow as well .②FRi increased with increasing spatial scales ,how‐ever FRoi showed a decrease as the scales increased .③ irrigation water use efficiency was slightly improved due to the relative few of the return flow reuse .Simulated results showed FRi raised by 6 .4% from the single field scale to the four-field scale .