The Spatially Explicit Load Enrichment Calculation Tool (SELECT) methodology was developed by faculty and staff in the Biological and Agricultural Engineering Department and Spatial Sciences Laboratory at Texas A&M University. Support for development was provided through a grant from the Texas State Soil and Water Conservation Board.

SELECT is an analytical approach for developing an inventory of potential bacterial sources, particularly nonpoint source contributors, and distributing their potential bacterial loads based on land use and geographical location. A thorough understanding of the watershed study area and potential contributors that exist is necessary to estimate and assess bacterial load inputs.

SELECT is a pathogen load assessment tool which can be combined with a watershed-scale water quality model using spatially variable governing factors such as land use, soil condition, and distance to streams to support Total Maximum Daily Loads (TMDLs) and Watershed Protection Plans (WPPs). This tool can be used to estimate the actual contaminant loads resulting in streams when used in conjunction with a fate and transport watershed model.

Visual outputs of SELECT allow a decision maker or stakeholder to easily identify areas of a watershed with the greatest potential for contamination contribution and enable the decision maker to use that information to help formulate management strategies.

About Load Duration Curves (LDCs)

A widely accepted and utilized approach for predicting whether pollutants are coming from point and/or nonpoint sources is the use of Load Duration Curve (LDC) analysis. An LDC is developed by first constructing a flow duration curve using streamflow data. Flow data are then multiplied by a threshold concentration (such as a desired target or an official water quality criterion) of a pollutant.