BASNYAT P, TEETER LD, FLYNN KM, LOCKABY BG
School of Forestry, Auburn University, Auburn, Alabama 36849-5126, USA
Environ Manage. 1999 May;23(4):539-549. doi: 10.1007/s002679900208.
/ Land-use activities affect water quality by altering sediment, chemical loads, and watershed hydrology. Some land uses may contribute to the maintenance of water quality due to a biogeochemical transformation process. These land-use/land-cover types can serve as nutrient detention zones or as nutrient transformation zones as dissolved or suspended nutrients or sediments move downstream. Despite research on the effects of individual land-use/land-cover types, very little has been done to analyze the joint contributions of multiple land-use activities. This paper examines a methodology to assess the relationships between land-use complex and nitrate and sediment concentrations [nonpoint source (NPS) pollutants] in streams. In this process, selected basins of the Fish River, Alabama, USA, were delineated, land-use/land-cover types were classified, and contributing zones were identified using geographic information system (GIS) and remote sensing (RS) analysis tools. Water samples collected from these basins were analyzed for selected chemical and physical properties. Based on the contributions of the NPS pollutants, a linkage model was developed. This linkage model relates land use/land cover with the pollution levels in the stream. Linkage models were constructed and evaluated at three different scales: (1) the basin scale; (2) the contributing-zone scale; and (3) the stream-buffer/riparian-zone scale. The contributing-zones linkage model suggests that forests act as a transformation zone, and as the proportion of forest inside a contributing zone increases (or agricultural land decreases), nitrate levels downstream will decrease. Residential/urban/built-up areas were identified as the strongest contributors of nitrate in the contributing-zones model and active agriculture was identified as the second largest contributor. The regression results for the streambank land-use/land-cover model (stream-buffer/riparian-zone scale) suggest that water quality is highest when passive land uses, such as forests and grasslands, are located adjacent to streams. Nonpassive land uses (agricultural lands or urban/built-up areas) located adjacent to streams have negative impacts on water quality. The model can help in examining the relative sensitivity of water-quality variables to alterations in land use made at varying distances from the stream channel. The model also shows the importance of streamside management zones, which are key to maintenance of stream water quality. The linkage model can be considered a first step in the integration of GIS and ecological models. The model can then be used by local and regional land managers in the formulation of plans for watershed-level management. KEY WORDS: Water quality; Land-use complex; Geographic information system; Nonpoint source pollution; Forested buffers
土地利用活动通过改变沉积物、化学负荷和流域水文状况来影响水质。一些土地利用活动由于生物地球化学转化过程可能有助于维持水质。当溶解或悬浮的养分或沉积物向下游移动时，这些土地利用/土地覆盖类型可作为养分滞留区或养分转化区。尽管对个别土地利用/土地覆盖类型的影响进行了研究，但很少有人分析多种土地利用活动的共同作用。本文探讨了一种评估土地利用复合体与溪流中硝酸盐和沉积物浓度（非点源污染物）之间关系的方法。在此过程中，划定了美国阿拉巴马州鱼河的选定流域，对土地利用/土地覆盖类型进行了分类，并使用地理信息系统（GIS）和遥感（RS）分析工具确定了贡献区。对从这些流域采集的水样进行了选定化学和物理性质的分析。基于非点源污染物的贡献，建立了一个关联模型。该关联模型将土地利用/土地覆盖与溪流中的污染水平联系起来。在三个不同尺度上构建并评估了关联模型：（1）流域尺度；（2）贡献区尺度；（3）溪流缓冲区/河岸带尺度。贡献区关联模型表明，森林作为一个转化区，随着贡献区内森林比例的增加（或农业用地比例的减少），下游的硝酸盐水平将降低。在贡献区模型中，住宅/城市/建成区被确定为硝酸盐的最强贡献者，活跃农业被确定为第二大贡献者。河岸土地利用/土地覆盖模型（溪流缓冲区/河岸带尺度）的回归结果表明，当森林和草地等被动土地利用类型位于溪流附近时，水质最高。位于溪流附近的非被动土地利用类型（农业用地或城市/建成区）对水质有负面影响。该模型有助于检验水质变量对距河道不同距离处土地利用变化的相对敏感性。该模型还显示了溪流边管理区的重要性，这是维持溪流水质的关键。该关联模型可被视为将GIS与生态模型整合的第一步。然后，地方和区域土地管理者可使用该模型来制定流域层面的管理计划。关键词：水质；土地利用复合体；地理信息系统；非点源污染；森林缓冲区
