Simulation of River Flow for Downstream Water Allocation in the Heihe River Watershed, Northwest China - Landscape Ecology for Sustainable Environment and Culture - page 167

Mainstream'', mandating water allocation to the lower reach each year (Pan and
Qian 2001 ; Feng et al. 2002 ). While a number of studies have been done in the
Heihe Watershed (Cheng et al. 1999 ; Feng et al. 2002 ; Pan and Qian 2001 ; Jia
et al. 2005 ), the magnitude, spatial and temporal distribution, and transfer mech-
anism of the Heihe hydrological system are still not well understood, especially in
the face of climate change and urbanization. This gap, together with the lack of a
comprehensive implementation plan has impeded the implementation of the State
Council's water allocation plan. This study uses a hydrological modeling approach
to address a key research question facing the Heihe River Watershed: how much
water flows from the middle reach to the lower reach annually to support com-
peting demands for water for domestic, irrigation, industrial supplies and reha-
bilitation of the ecosystems under the current climatic conditions?
Specifically, this study simulates the hydrological processes of the upper and
middle reaches of the Heihe River Watershed to determine the amount of water
flowing downstream annually from the middle reach (at Zhengyixia Gage Station).
It describes our collaborative work to adapt the Distributed Large Basin Runoff
Model (DLBRM) to the Heihe Watershed for understanding the hydrological
processes of the river system and thereby provides partial basis for implementation
of the central government's water allocation plan. We first describe the physical
features of the Heihe watershed, then briefly introduce the structure, input, and
output of the DLBRM, and finally discuss the simulation results of the DLBRM in
the Heihe River Watershed.
9.2 Methods
9.2.1 The Study Area
The boundary of the Heihe River Watershed is shown in Fig. 9.1 . The Qilian
Mountain is situated at the south of the watershed, with a peak elevation of
5,584 m. Ice and snow cover it year round above 4,500 m. Mixed alpine meadow
and permafrost dominate between 3,600 to 4,500 m. While the main vegetation is
forest and grassland with a mean annual precipitation of 250-500 mm in the
1,900-3,600 m range, the landscape below 1,900 m is dominated by hilly or
grassland desert with a mean annual precipitation of 200-250 mm (Pan and Qian
2001 ; He et al. 2009 ). Located in the middle reach of the Heihe Watershed, the
Hexi Corridor hosts over 90 % of the total agricultural oases in the watershed and
supports more than 97 % of the Heihe River Watershed's 1.8 million inhibits in
two metropolitan areas: Zhangye (population 1.25 million in 2000) and Jiuquan
(population 0.49 million in 2000). Irrigation supply is from both surface water
withdrawals and groundwater pumping. North of the Hexi Corridor is the Alashan
Highland (the area north of Zhengyixia Gage Station with mean elevation
1,000 m), an extremely dry desert with an annual precipitation below 50 mm.