L-THIA estimates changes in recharge, runoff, and nonpoint source pollution resulting from past or proposed development. It estimates long-term average annual runoff for land use and soil combinations, based on community-specific long-term climate data. In the basic model, the only inputs are: location (state and county), soil type in area where the land use will occur (available online if unknown), and type and size of land use change (e.g., 100 acres of agricultural land converted to 50 acres high-density residential and 50 acres commercial). L-THIA will generate estimated runoff volumes and depths, and expected nonpoint source pollution loadings to water bodies. Results can be displayed in tables, bar graphs, and pie charts. More advanced models are available.