Abstract
In order to reduce the environmental and ecological problems induced by water resources management and use, this paper proposes a concept of environmenta water requirement. It is defined as the minimum water amount to be consumed by the natural water bodies to conserve its environmental and ecological functions. Based on the definition, the methods for calculating the amount of environmental and ecological water requirement are determined. In the case study on Haihe-Luanhe river system, the water requirement is divided into three parts, i.e., the basic instream flow, water requirement for sediment transfer and water consumption by evaporation of the lakes or everglades. The results of the calculation show that the environmental and ecological water requirement in the river system is about 124x108 m3, including 57x108 m3 for basic in-stream flow, 63x108 m3 for sediment transfer and 4x108 m3 for net evaporation loss of lakes. The total amount of environmental and ecological water requirement accounts for 54% of the amount of runoff (228x108 m3). However, it should be realized that the amount of environmental and ecological water requirement must be more than that we have calculated. According to this result, we consider that the rational utilization rate of the runoff in the river systems must not be more than 40%. Since the current utilization rate of the river system, which is over 80%, has been far beyond the limitation, the problems of environment and ecology are quite serious. It is imperative to control and adjust water development and utilization to eliminate the existing problems and to avoid the potential ecological or environmental crisis.
Highlights
River system, to some extent, can be regarded as an independent eco-system, which includes river channels, lakes and the lands near the water bodies
Three parts are decomposed in calculating the total amount of the water requirement, namely, (1) the basic in-stream flow, which is the minimum amount of water needed for protecting the most primary environmental and ecological function of the rivers; (2) water for sediment and solute transfer, which is part of water required to transfer sediment and salt in a certain situation to keep the dynamic balance of the river system; and (3) water consumed by lakes and everglades, which refers to water evaporation in the lakes and everglades in order to maintain their general function
In the history of water utilization and development, our attention was mainly paid to the benefits we got from rivers, whereas the environmental and ecological functions of the river system used to be neglected
Summary
To some extent, can be regarded as an independent eco-system, which includes river channels, lakes and the lands near the water bodies. In the aspect of water resources development and utilization in China, water requirement for environment and ecology has been ignored for decades of years, when attention was mainly paid to the agricultural, industrial and domestic water use. It is just because of this ignorance that water environment and aquatic eco-systems have been seriously devastated and the degradation of water bodies has been accelerated with the renewability of water resources seriously threatened, which has aggravated water resources crisis. Since there is not enough water in the natural water bodies to meet the environmental and ecological water demand in many places in the system, a series of environmental and ecological problems such as the shrinkage of river channel, the degradation of water quality etc., have occurred, and even some perennial rivers have become seasonal ones (Liu Changming & Wei Zhongyi, 1989; Yu Fenlang et al, 1994; Fang Ziyun, 1993; Wu Kai and Xu Yuenxian, 1997)
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