How does changing land use in a watershed typically affect surface water quality?

Changing land use in a watershed typically impacts surface water quality predominantly by increasing runoff and pollution. When land use shifts, for example from forests or wetlands to urban areas or agricultural land, the natural absorption and filtration processes that normally take place are disrupted.

Urbanization leads to more impervious surfaces, such as roads and buildings, which prevent water from being absorbed into the ground. This increases the amount of surface runoff during rainfall events, causing more water to flow into rivers and streams quickly. Consequently, this runoff often carries pollutants like sediments, nutrients (from fertilizers), and chemicals (from pesticides and urban litter) into nearby bodies of water. The result is a deterioration in water quality, which can lead to issues like algal blooms, decreased oxygen levels, and harm to aquatic life.

In contrast, the other options do not accurately reflect the typical consequences of land use changes in a watershed. For example, while certain land use changes could theoretically enhance wildlife habitats, this is not a universal outcome and is context-dependent. Similarly, changing land use does not inherently increase available freshwater or enhance water clarity; rather, it often has the opposite effect on water clarity due to increased sediment and pollutant levels.