The purpose of this dissertation was to examine the association between the spatial patterns of urban land uses and surface water quality parameters at the watershed outlet. The aim of the study was to understand the strength and nature of this relationship, and examine new methods of classifying and quantifying contributing urban land-uses and their spatial patterns. The hypothesis of this research was: in an urban watershed, the variation in the spatial patterns of contributing land uses will have a significant impact on the surface water quality parameters at the watershed outlet.This relationship between urbanization and water quality is important terms of understanding and managing urban growth to preserve water resources, especially in dry, arid regions. The outcome of this study will establish and define relationships between patterns of urban land uses and surface water quality parameters at the watershed outlet. Policy makers, watershed managers, and land-use regulators may have special interest in understanding these relationships to develop sustainable urban growth strategies.The urban area of the Las Vegas Valley Watershed was used as a case study to test the research hypothesis. Existing water quality monitoring stations on the four major tributaries to the Las Vegas Wash were used to define four independent watersheds. Geographic Information Systems (GIS) was used to geo-reference water quality monitoring stations and to delineate contributing watersheds at each sampling point. Rainfall events leading to water quality sampling were used to derive contributing landuses within each watershed. The association between the total amount, types, patterns of contributing land uses, and surface water quality parameters at the watershed outlet were tested using Pearson correlation.Correlation results showed very clearly that total amount and types of the contributing land uses cannot fully explain by themselves the variations in the surface water quality parameters at the watershed outlet. Further analysis of the association between the spatial patterns of the contributing land uses and the water quality parameters showed some of the measured water quality parameters to be more sensitive to changes in the spatial patterns of the overall contributing land uses.Two different patterns of contributing land uses were identified: (1) fragmented pattern, the distribution is characterized by a large number of smaller patches, spread across the landscape, and (2) clustered pattern, the distribution is characterized by a smaller number of larger patches in close proximity to each other.We found that some of the water quality parameters, such as TDS, TKN, total N, BOD, and COD to be positively correlated with landscapemetrics describing fragmentation (pH was negatively correlated). The trend for the same parameters was opposite when compared to metrics describing clustered patterns. These results indicated that there is a significant association between water quality parameters at the watershed outlet and the spatial patterns of the contributing land uses.Additionally, this study illustrates that using people oriented land-use classification method, which is based on the actual use of the land ismore appropriate for highly urbanized areas compared to the resource oriented method, which is based on remotely-sensed data and often used for land use and land cover classification.
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