Documentos y Trámites

Nonpoint source reductions can be achieved through the implementation of management measures that can reduce loads by integrating appropriate land use policies and BMPs. The relation of topography and land use is important in understanding of nutrients occurrence. Land use BMPs provide important opportunities to reduce pollutants in runoff by integrating water quality concerns into the application of land use practices. The use of BMPs represents one of the most effective pollution

prevention practices. Nutrients concentrations in stream base flow are unlikely to change quickly in response to land-management practices. It may take years for some ground water to reach streams. The ground water under the agricultural land contains contaminants from the agricultural land use, but contaminants may be absorbed by vegetation or diluted as the water passes under the forested areas on the way to the stream (USGS, 1998).

Best Management Practice can control effectively movement of pollutants, prevents degradation of soil and water resources, and is compatible with the land use.

BMPs could include an array of practices to increase water infiltration that could be applied to agricultural areas, residential development, industrial sites, and constructions.

Agricultural runoff contains pollutants including nutrients, sediment, animal wastes, salts, and pesticides. Many practices can be used to control runoff and reduce the erosion and transport of sediment from agricultural fields (USEPA, 2006).

BMPs to reduce agricultural and urban impacts may include vegetative management practices such as conservation tillage, contour farming, strip cropping, filter strips, vegetated field borders, shoreline revegetation, shoreline stabilization,

cover crops, crop rotation, pasture management, urban forestry and urban practices such as porous pavement and water quality inlets. They may also consist of different

structural practices such as water and sediment control basins, roof water collection devices, tree filter strips, terraces, diversions, grassed waterways, woodland fencing and wetland development.

The three hypotheses of the study are confirmed at least to a certain degree:

spatial and temporal changes in land use have significant effects on the water quantity in a watershed ecosystem; the nature of spatial patterns in water quality in a watershed are influenced by temporal transitions and spatial influences; dynamic modeling is superior to static models of land use change in watersheds.

2.6 CONCLUSIONS

Urbanization and human population tends to grow and place demands on natural resources. Human activities can have a dramatic impact on water resources in the

Blackstone River watershed. Management of these resources and land areas is important for maintaining natural resources. With continued urban growth policies in management is necessary for wise use of the watershed resources. Dynamic simulation modeling is used to simulate changes that may occur to a subwatershed in Blackstone river

watershed.

This research simulates both the dynamic and spatial behavior of the watershed system, and models important subwatershed level variables in the system, such as land use types, soil loss levels, runoff volumes. Dynamic modeling is used to study system variability in space and time. The model is run over 100 years. The simulation model is

designed to assess potential land use change, specifically to address questions about how the ecosystem responds to the changes at a subwatershed scale. The model is object-based and modular to represent Patch, Neighborhood, and Soil Loss and Runoff.

Four major land-use types are evaluated in two critical dimensions—time and space.

The land-use is determined by environmental factors such as soil characteristics, climate, topography, and vegetation to understand past changes in land use and project future land-use trajectories.

The overall results show that land use modeling requires improved knowledge of the factors that determine land use change. Spatial and temporal changes in land use have significant effects on a watershed ecosystem. The nature of spatial patterns is influenced by temporal transitions and spatial influences. Understanding the past and future impacts of changes in land cover is central to the study of land use change impacts on watershed system components. The modeling results show that the increase in urban land use in the watershed is associated with the decline in agricultural and forest land and urbanization could become a serious problem in the future. The results emphasize the need to protect agricultural area in rapidly changing watersheds. The highest soil loss is associated with agriculture and urban areas, while forested areas had lower soil loss: the highest runoff areas are associated with urban and agriculture types and the low runoff areas with forest type. There is the evidence that highest runoff and soil loss areas are associated with agriculture and urban land use. This problem can be related to a weak land use planning regulations where land use policies reforms can be required. There is also the need to implement planning regulations to limit adverse

environmental impacts of urban expansion. The overall results show that neighborhood interactions and spatial policy are important spatial drivers of land use change.

The relation of topography and land use is important in understanding of water quality. The land use BMPs are an important opportunity to reduce pollutants in runoff by using an effective planning process to integrate water quality concerns into the development and redevelopment of land use processes.

This study develops a methodology that integrates modeling and analytical procedures in the land use change prediction at a subwatershed scale. The calibration and validation of the simulation model is used to minimize errors from parameters measurements and developed equations specified for a system. They can minimize errors. The conceptual limitations of the model are that the number of patches that can be processed in the model is limited to a certain amount. The further development of the model makes it possible to include variables to calculate fragmentation and

undeveloped land. Further extensions of this research could also focus on testing different policies and best management practices. More research is also needed in the area of how to determine the most effective policies and practices for the minimizing negative effects of the watershed impairment in regard to land use change.

This thesis adds new knowledge to watershed literature through assessment of impacts of land use changes on the watershed’s landscape. It also helps provide a method that allows for a spatial dynamic analysis of a land use change and assessment of spatial interactions at a subwatershed scale. Watershed ecosystem components and the dynamic nature of interactions in a watershed ecosystem is a focus of this study.

CHAPTER 3