Introduction to Nutrient Pollution:
Although nitrogen and phosphorus are essential elements for life, they are considered water quality contaminants because human activity has increased their abundance far above natural levels. When these nutrients are present in high concentrations in aquatic ecosystems, they can cause algal blooms and subsequent oxygen depletion during decomposition. Because many aquatic animals depend on oxygen to live, this can create “dead zones” and fish kills.
I am focusing my research on phosphorus (P) pollution, which is more of a problem in fresh-water systems such as lakes and some estuaries. While there are many sources of P pollution, my research has focused on agricultural sources, and specifically, developing models that can help us determine management practices that will restrict the movement of P into water bodies.
Before we can model the movement of P, we first need to have a reliable watershed model that is capable of determining where runoff is generated on the landscape. I have been working with the VSLF model, which uses the curve number method in conjunction with a daily water balance to determine runoff. We can then redistributed the runoff to areas of the landscape that we expect to saturate based on the Soil Topographic Index (STI), calculated from elevation, contributing area, and soils information. The areas of the watershed that we expect to generate runoff are at highest risk for transporting pollutants – we have created a tool for the Owasco Lake Watershed in NY that allows residents to see areas that we expect to be most sensitive to polluting activities in the next three days.
An important component of any watershed model is evapotranspiration (ET). Evapotranspiration is driven by the atmospheric potential to convert liquid water to a gas (often referred to as Potential Evapotranspiration, or PET), and the amount of water available in watershed (we can estimate this using a water budget approach). Unfortunately, PET is difficult to model because ideally we would need to know radiation and wind speed in addition to more readily available data such as precipitation and temperature. I am interested to know if we can more accurately model PET in watersheds where radiation and wind data are not available, by estimating components of the radiation budget.
Using a watershed model that can distributes the runoff to those areas most likely to saturate, we can then estimate P transport based on the soil P and manure/fertilizer application to these wet areas. I hope to validate a phosphorus model that predicts P in runoff based on manure spreading, and better understand the processes that drive P release and retention in the soil.