海河流域生态需水核算

Primary estimate of ecological water requirement in Haihe Basin

从生态系统角度分析了生态需水内涵和生态需水与生态用水概念的差别。探讨了海河流域自然陆地、河流、湿地、城市 4种生态系统类型生态需水核算方法 ,并对其生态需水量进行了核算。大气降水首先被天然植被利用后形成地表径流 ,才能被人类管理利用来满足经济水量和生态水量需求。从水资源管理来说 ,河流、湿地、城市等生态需水来源于径流性水资源可称为狭义生态需水 ,而包括利用降水性水资源的天然植被生态需水在内的全部生态系统生态需水可认为是广义的生态需水。狭义生态需水是水资源管理及生态需水研究和关注的重心。研究结果表明 :海河流域河流生态需水 31.6 4× 10 8m3,占多年平均天然径流量的 12 % ;湿地生态需水为 34.31× 10 8m3,占 13% ;城市生态需水量 10 .83× 10 8m3,占 4 .1% ,3项合计占径流总量的 2 9.1%。生态需水量是一个动态的值 ,随生态保护目标的提高和经济的发展核算结果必然发生变化 ,维护生态环境质量的状况不同 ,也存在最大、最小生态需水量的阈值问题 。

Water resources are the base of all life-system on the world. The demand for water from China's growing population is creating an ever-increasing pressure on the country's rivers and other ecosystems. The urgent need for domestic, agricultural and industrial water uses often conflicts with the water demand to maintain or improve ecosystem function. The allocation of water to sustain natural ecosystems, to restore rivers degraded by over-abstraction and to protect ecosystem services has become a key issue in water resource management in our country. Haihe basin is located in a semi-arid region and, with a mean rainfall of 548 mm, less than the whole country average of 648 mm and the global average of 800 mm. Combinations of socio-economic and political factors, together with a growing population have multiplied the effects on water resource scarcity. Without consider ecological water requirements in water resources management is one of the reason of deterioration of the ecological condition. The challenge therefore, has been to determine ecological water requirements for all the ecosystems. In this paper, the estimate method and total amount of ecological water requirement of four ecosystems were studied, such as natural terrestrial, river, wetland and urban ecosystems. The precipitation, from atmosphere fall to the earth, first incepted by natural vegetation before producing surface runoff. People can manage the remained water resources to meet the requirement of economic water demand and ecological water demand. Considering water resources management, the ecological water requirement of river, wetland, urban ecosystem which comes from runoff water resources can be defined as narrow sense of ecological water requirement. And natural terrestrial ecosystem ecological water requirement that including precipitation may be called general ecological water requirement. The narrow sense of ecological water requirement is the key issue of the water resource management and ecological water requirement estimation. The result showed that: in Haihe Basin the amount of ecological water requirement of river, wetland and urban is 31.64×10~8m^3, 34.31×10~8m^3, 10.83×10~8m^3, respectively, which account for 13%, 4.1%, 29.1% of the annually average natural runoff , respectively. Ecological water requirement is defined as the water regimes needed to sustain the ecological values of ecosystems at low levels of risk. Ecological water provisions are the water that can be maintained or made available in an attempt to meet the ecological water requirements. This pilot study will concentrate on determining the ecological water requirements. The amount of ecological water requirement is a dynamic value, which strongly depend on ecological protection targets and economic development. A maximal and minimal ecological water requirement can be estimated under different aims of eco-environment quality in future.