Streamflow allocation in arid watersheds: a case study in Northwestern China

Abstract. This paper proposes a framework for allocating water resources among the upper, middle, and lower reaches of arid watersheds to meet the multiple demands for water, including rehabilitation of downstream ecosystem. The framework includes: (1) hydrologic simulation of distribution of water resources in the study watershed; (2) development of water allocation criteria; and (3) implementation of the water allocation plan. The advantages of the proposed framework are: (1) spatial integration; (2) multiple objectives; (3) incorporation of local needs through participatory decision making; and (4) dynamic evaluation.

The framework was applied to the Heihe watershed, a large inland (terminal lake) watershed with a drainage area of over 128 000 km² in Northwestern China. Simulation of the daily river flows for the period of 1990–2000 by the Distributed Large Basin Runoff Model shows that Qilian Mountain in the upper reach produced most of the runoff in the watershed, and the increased withdrawals of water for agricultural irrigation, industrial development, and municipal supplies at the middles reach oasis reduced the annual mean discharge by approximately 0.18 × 10⁹ m³ over the simulation period, making the middle reach unable to deliver the mandated amount of 0.95 × 10⁹ m³ water downstream by the State Council, under normal climatic conditions. Changes in land use practices need to be implemented to achieve the mandated water allocation plan. The paper suggests that a participatory watershed planning approach involving multiple stakeholders in the water allocation process be undertaken to address key questions regularly, including how much water should be allocated to what uses and for whom and at what price?