Relationships Between Landscape Characteristics and Nonpoint Source Pollution Inputs to Coastal Estuaries

Area of Science:

• Environmental Science
• Hydrology
• Ecology

Background:

• Land-use activities are primary drivers of water quality degradation through altered sediment and chemical loads.
• Existing research often overlooks the combined effects of multiple land-use types on water quality.
• Understanding the joint impact of land-use complexes is crucial for effective watershed management.

Purpose of the Study:

• To develop and evaluate a methodology for assessing the relationship between land-use complexes and stream water quality.
• To quantify the contributions of various land-use types to nonpoint source pollution, specifically nitrate and sediment concentrations.
• To analyze these relationships at multiple spatial scales: basin, contributing zone, and riparian zone.

Main Methods:

• Utilized geographic information system (GIS) and remote sensing (RS) to delineate basins, classify land-use/land-cover types, and identify contributing zones in the Fish River, Alabama.
• Collected and analyzed water samples for physical and chemical properties to determine pollutant concentrations.
• Developed and evaluated linkage models at basin, contributing-zone, and stream-buffer scales to relate land use to water quality indicators.

Main Results:

• Forests act as nutrient transformation zones, with increased forest cover correlating to decreased downstream nitrate levels.
• Residential/urban/built-up areas were identified as the largest contributors of nitrate, followed by agricultural lands.
• Passive land uses (forests, grasslands) adjacent to streams improved water quality, while non-passive uses (agriculture, urban) negatively impacted it.

Conclusions:

• The developed linkage model effectively relates land use/land cover to stream pollution levels at various scales.
• Streamside management zones with passive land uses are critical for maintaining stream water quality.
• The methodology provides a foundation for integrating GIS and ecological models for watershed-level management planning.