Multi-objective optimization approach for land use allocation based on water quality criteria

Surface water contamination by point and nonpoint sources of pollution is a major concern for public and government agencies around the world due to the excessive contamination of water bodies. Water is an important resource for any community to support life, economic development, recreation facilities, and aesthetic values. According to estimates by the United States Environmental Protection Agency (USEPA), about 40% of the monitored national water supplies does not meet established quality standards. For Puerto Rico, the 2002 water quality inventory reports 70% of monitored river miles impaired (PREQB, 2002). Sediment loadings and nutrients concentrations are one of the major contaminants reaching water bodies producing serious consequences in ecological systems, human health, water provisioning, and recreational activities. Additionally, the list of impaired waters of Puerto Rico states that all the reservoirs fail to meet existing aquatic life criteria for dissolved oxygen resulting in an eutrophication condition characterized by an elevated nutrient levels status (PREQB, 2003).;Puerto Rico is facing the need to develop and implement Total Maximum Daily Loads (TMDL's) for impaired lakes and rivers listed by the USEPA. As part of the efforts to reduce and mitigate the pollution issue, this investigation is presented to evaluate the Rio Grande de Arecibo watershed, located in the north-central Puerto Rico using an integrated land use planning methodology at the watershed.;The integrated land use allocation scheme developed in this research consist firstly of a water quality analysis and simulation for a ten years period (1995-2005) using the Hydrological Simulation Program Fortran (HSPF). The watershed simulation includes the hydrology, sediments, and nutrients components (Total Nitrogen species and Total Phosphorus). These variables will provide data to generate the annual loadings and annual export coefficients intervals of the species by land use in the watershed and are used as input in the second stage of the methodology.;The second stage of this research consists of a multi-objective optimization approach using the Multi-objective Linear Programming (MOLP) method and taking into account the inherent uncertainty associated with the watershed in terms of hydrometeorological, physical, and socio-economic conditions. For this reason, the land use export coefficients intervals were used as input for the decision variables in the MOLP model. A total of six different hypothetical scenarios were evaluated reflecting possible conditions in the future growth pattern at the watershed in the time study horizon (year 2025).;Complementing the previous stages, a Geographical Information System (GIS) was developed for the optimal land use suggested ranges allocation from the MOLP model. This part of the research incorporates the concept of spatial optimal units based on the constraints in the watershed from a spatial point of view and seeks for the available areas that comply with the MOLP requirements. At this stage, additional constraints were incorporated in the land use integrated planning methodology responding to physical and socioeconomic characteristics in the study area.;Finally, the watershed integrated land use planning methodology is combined with an analysis and evaluation of institutional, political, fiscal, and environmental indicators for municipalities that integrates the Rio Grande de Arecibo (RGA) watershed. This component allows defining the environmental capability of each municipality in order to forecast successful level in the implementation of the complete methodology suggested by this research in terms of optimal land use planning.;Findings of this research will provide the base work to find possible solutions to difficult issues related to land use planning for preservation, forestry, agriculture, and urban development while maintaining the viability of water quality and quantity. The final purpose of this research is not to designate a particular landuse for an area within RGA, rather, it is to establish the landuse distribution within RGA that help the municipalities comply with USEPA and the Puerto Rico Environmental Quality Board (PREQB) water quality standards.;Puerto Rico is one of the most densely populated countries in the world, consequently has the future conditions of many locations around the world with limited land resources and a very high population density that demands jobs, infrastructure, and housing. The proposed methodology offers a unique way to incorporate modeling approaches for watershed management, individual system components and the administrative capability of participating municipalities.