The Arroyo Colorado is a 90-mile long perennial stream within the Nueces-Rio Grande Coastal Basin in southern Texas. About 25 miles of the stream serves as a floodway for the Rio Grande. The lower third provides an inland waterway for commercial barge traffic and a recreational area for swimming, boating and fishing. Near the Gulf coast, the Arroyo Colorado serves as an important nursery and foraging area for numerous species of marine fish, shrimp and crab. The Arroyo Colorado Watershed (ACW) covers approximately 700 square miles and includes parts of Hidalgo, Cameron, and Willacy Counties in Texas. Predominantly agricultural, the ACW receives irrigation water from the Rio Grande through a system of irrigation districts using a network of canals, ditches and pipes. Urbanization is extensive in the western and central parts of the ACW, with major cities in Mission, McAllen, Pharr, Donna, Weslaco, Mercedes, and Harlingen.
Description of Decicsion Making Problem
Perennial streamflow in the Arroyo Colorado is primarily sustained by effluent from municipal wastewater treatment plants. Irrigation return flows and point-source discharges supplement the flow on a seasonal basis. Since 1978, the eastern, tidally-influenced portion of the Arroyo Colorado has been included on the Texas list of impaired water bodies (according to the Clean Water Act Section 303(d)) due to occurrence of low dissolved oxygen concentrations. Oxygen depletion has been attributed to excessive loading of nutrients—nitrogen and phosphorus compounds— from both point sources (mainly municipal wastewater treatment plant discharges) and nonpoint sources (primarily through agricultural runoff). To address this impairment, the ACW Partnership developed the ACW Protection Plan (ACWPP) in 2006.
Implementation of the first phase of ACWPP is under way and is scheduled to run until 2015. Designed to reduce nutrient loading as well as improve natural habitat in the watershed, the key decisions in the ACWPP have included building new wastewater treatment plants and upgrading existing ones, connecting tens of thousands of low-income (colonia) residents to sanitary sewer systems, adopting agricultural best management practices (BMPs) on irrigated croplands, and developing Storm Water Management Programs for several urban areas in the ACW. The Texas Commission on Environmental Quality (TCEQ) is supporting the ACW Partnership in implementation of the ACWPP.
CGDSS (Collaborative Geospatial Decision Support System) is a multiyear project funded by NASA Earth Science for Decision Making: Gulf of Mexico Region
. The primary goal of the CGDSS is to develop a geospatial DSS to support decision making activities by TCEQ and the ACW Partnership in implementing the ACWPP. Specific objectives of CGDSS are
- Integrate the main components of water quality decision-making process using webGIS and content management systems,
- Optimize the use of remotely sensed Earth observations and in-situ data,
- Enable implementation tracking, and
- Create a venue for stakeholder participation.
The Maps module uses state-of-the-art webGIS technologies to provide visualization of geospatial features of the ACW. Geospatial information is acquired from local servers and remote servers through web map service (WMS) . Locally served layers can be edited through the backend Admin interface enabled by the geospatial content management server.
The Analyses module includes two submodules: (i) SWAT, a user interface for displaying nutrient load based on SWAT model outputs; and (ii) PLOAD, a simple, first-order analytical tool for calculating nonpoint source pollutant loadings using export coefficient estimated from SWAT model outputs.
The News module aggregates news related to ACW by subscribing to multiple Rich Site Summary (RSS) feeds.
The Admin provides an interface for authorized users to manage CGDSS content.
Expected Point Loadings from Implementation of the ACW Protection Plan (tons)