Simulation of River Flow for Downstream Water Allocation in the Heihe River Watershed, Northwest China - Landscape Ecology for Sustainable Environment and Culture - page 166

Mountain in the upper reach area was the main source of runoff generation in the
Heihe Watershed, and annually, the Heihe River discharged about 1 9 10 9 m 3 of
water from the middle reach (at Zhengyixia Gage Station) to the lower reach under
the normal climatic conditions (with a likelihood of 50 %). These flows are
consistent with the State Council's mandate of delivering 0.95 9 10 9 m 3 water
downstream annually. However, the river flow would be significantly less under
the dry climatic conditions, making it much more difficult to deliver the mandated
amount of water downstream for ecosystem rehabilitation.

demands Distributed

Keywords Multiple water large basin runoff model

(DLBRM) The Heihe watershed Northwest China Water shortage

9.1 Introduction

Proper management of the limited water resources is essential to ensure the
welfare of human beings and the sustainability of dry land ecosystems, which
support over 38 % of the world population (Reynolds et al. 2007 ). During the past
few decades, however, improper water resource management has resulted in
numerous problems worldwide, including poor food security, increased human
diseases, conflicts between different users, limitations on economic development
and human welfare, desertification, salinization, sand storms, water pollution, and
so forth (UN World Water Development Report 2003 ; Reynolds et al. 2007 ). In
China, the increased withdrawals from the upper and middle reaches of the Yellow
River depleted groundwater in much of the basin and contributed to desiccation
(i.e. no measurable flow in the river) of the lower reaches in 22 of the years
between 1972 and 2000. This desiccation has created serious economic and
environmental problems throughout the North-Central China, including water
rationing, under-capacity industrial production, reduced crop yields, water pollu-
tion, wildlife habitat depletion, coastline recession, and sea water intrusion (He
et al. 2005 ). In arid Northwest China, irrigated farming accounts for more than
80 % of total water usage. Over the past few decades, the increased withdrawals
for agricultural irrigation and municipal water supplies in the Hexi Corridor of the
Heihe River Watershed (the second largest inland river or terminal lake in the
nation, with a drainage area of 128,000 km 2 ) since the 1970s have depleted much
of the river flows to the lower reach, shrinking the East Juyan Lake and drying up
the West Juyan Lake, endangering aquatic ecosystems, accelerating desertifica-
tion, intensifying water conflicts between the middle reach of Gansu Province and
lower reach of the Inner Mongolian Autonomous Region (IMAR), and damaging
relationships among Han, Mongolian, and Hui ethnic groups (He et al. 2009 )
(Fig. 9.1 ). To mitigate the water conflicts and rehabilitate West Juyan Lake, the
State Council of the People's Republic of China (the executive branch of the
central government) has issued a ''Water Allocation Plan for the Heihe Watershed