Groundwater systems are an important part of the world's ecosystems, linking the lithosphere, atmosphere, hydrosphere, and biosphere. Groundwater is the dominant factor influencing vegetative community distribution patterns in the arid and semi-arid regions of Northwest China. Also, groundwater is the primary source of water for human uses in North China. With recent economic growth, the region is experiencing rapid development of its groundwater resources. The groundwater has been and is being seriously depleted and the system is displaying some unstable characteristics and vulnerabilities, which are significantly impacting the ecology of the area.
Various types of sensitivity assessment are often used to study the stability of a region's environment and ecology. A groundwater ecological sensitivity assessment can be used to facilitate protection of the environment and to encourage sustainable development of groundwater resources. This paper provides a case study of the Lower Liaohe River Alluvial Plain, which is in the most economically developed region of Liaoning Province. The area is experiencing a significant water shortage.
First, groundwater ecological sensitivity and its attributes were defined. Twenty-two factors were selected to be used in constructing the assessment indicator system. These were based on five aspects of groundwater quality and quantity including: 1) characteristics of the local groundwater system, 2) natural conditions in the region, 3) external pressures including human-caused pressures, 4) resources available and conservation, and 5) the local ecological environment. These factors were designed based on actual conditions of the area studied and took into account a variety of indicators including spatial scale, dominating environmental conditions, independence from other factors, sensitivity of the local groundwater resources to impacts, early warning signs of problems within the groundwater system, the cumulative impact of qualitative and quantitative factors, practicality of use factors, a need to standardize the data, and classification of various factors and impacts on ground water resources. Each factor was defined and described. The sensitivity of groundwater in relation to each factor was ranked on a scale of one to five, defined as 1) insensitive, 2) slightly sensitive, 3) moderately sensitive, 4) highly sensitive, and 5) extremely sensitive groundwater conditions. The assigned value for each indictor was determined by reviewing related standards and references.
Once the various indicators or factors were defined and standardized, a groundwater ecological sensitivity assessment in the Lower Liaohe River Alluvial Plain was carried out. First, the sensitivity of the five aspects of groundwater quality and quantity were evaluated individually by applying spatial analysis of a geographic information system and the distribution of the five factors listed above was analyzed. Second, an integrated sensitivity value was calculated using a weighted model from GIS for water quantity and water quality.
For water quantity, the results show the slightly and moderately sensitive areas of water quantity dominate and comprise 65.14% of the study area. The entire study area was classified as 5.35% insensitive to water quantity issues, 40.53% slightly sensitive, 24.61% moderately sensitive, 21.64% very sensitive, and 7.87% extremely sensitive. For water quality, moderately and highly sensitive areas of water quality dominate and compose 86.56% of the study area. The entire study area was classified as 1.11% insensitive to water quality issues, 10.99% slightly sensitive, 50.17% moderately sensitive, 36.39% very sensitive, and, 1.34% extremely sensitive. When sensitivity to both water quantity and water quality issues are considered, areas of moderate or higher sensitivity for both quantity and quality occupy more than 59.62% of the entire research area, indicating the degree of ecological sensitivity is generally high and groundwater resources are very vulnerable. The analysis of the spatial distribution of the five zones shows the insensitive and slightly sensitive zones are mainly distributed in the Xinmin-Liaozhong plain of the eastern alluvial floodplain. Moderately sensitive zones are mainly distributed in the middle plain and western low mountain region. The highly and extremely sensitive zones are mainly distributed in cities of Liaoyang and Fushun, and in the mountains surrounding the plain.