Basin-wide evapotranspiration management: Concept and practical application in Hai Basin, China

As the demand for water resources continues to grow, the current “demand management” approach often fails to deliver the expected results in terms of reduced water consumption, release of water to other uses, or improved environmental conditions. Recognizing that evapotranspiration (ET) represents the dominant consumptive use of water in the hydrologic cycle, this paper describes an approach to basin-scale water resources management based on ET. The ET management approach comprises four stages: (i) a basin-scale water consumption balance; (ii) determination of a target ET consistent with sustainable water consumption; (iii) identification of water consumption tradeoffs, competition and feedback among different water sectors (agricultural, industrial, domestic, and socio-environmental); and (iv) basin-wide monitoring of sustainable water consumption. Continuous, basin-wide ET data obtained from the ETWatch models are combined with estimates of water consumption as a result of mechanical, chemical, and biological energy to assess the water consumption balance, and set targets. On this basis, water resource managers can identify opportunities to achieve sustainable, productive use of water resources by (i) reducing non-beneficial ET; (ii) converting non-beneficial ET to beneficial ET; and (iii) increasing the productivity of beneficial ET. Irrigated agriculture is usually the largest controllable contribution to ET in a basin, so meeting the target ET for agriculture is key. A water balance analysis for Hai Basin and the implementation of ET management in the Basin are presented to illustrate the ET management approach.