Watershed Approach: Land Use Effects on Water Quality and Quantity

Introduction

Land use and water resources are unequivocally linked. The type of land and the intensity of its use will have a strong influence on the receiving water resource. Whether the source is natural or comes from a human activity, the impact of any land use practice on either the quantity or quality of water can be substantial.

In general, the water quality across the United States and in Michigan has improved over the last 20 years. The combination of regulations, best management practices, and a renewed stewardship ethic has been helpful in controlling many problems that had previously resulted in a decline in water quality or a decrease in water availability. However, an increasing population, developmental pressures, absence of land use planning, and competition for water resources, continually contribute to the degradation of water resources. Managing water resources on a watershed basis will help address potential impacts including:

changes in water flow and storage which may lead to floods, drought, or changes in microclimate

deterioration of water resources due to lack of soil conservation and increased input of pollutants

decline in water resources due to excessive use (overexploitation)

increases in soil erosion and salinization due to poor land use practices

(Vink 1983)

This module will address water resources and associated land uses by exploring the interrelationships between human activity on the land and the impacts to both the quality and quantity of water.

Land Use and Land Cover

Land use and land cover have a direct relationship with environmental characteristics and processes, including the productivity of the land, species diversity, climate, biogeochemistry and the hydrologic cycle. The characteristics of land cover and use have an impact on the climate, biogeochemistry, hydrology, and the diversity and abundance of terrestrial species.

What is Land Cover?

Land cover refers to the type of feature present on the surface of the earth. For example, agricultural fields, lakes, rivers, pine forests, roads, and parking lots are all land cover types. Land cover may refer to a biological categorization of the surface, such as grassland or forest, or to a physical or chemical categorization such as concrete.

Land cover is denoted by the physical state of the land, including the type and quantity of vegetation, water and earth materials. Land cover change occurs when one land cover type is converted to another, or is modified, such as a change in agricultural composition. Land cover is continually influenced by land use due to human cultural, social, and economic activities. Understanding the significance and potential consequences of land cover changes for climate, biogeochemistry, or ecological complexity is difficult without land use information.

How do Land Cover and Land Use Relate?

Land use refers to the human purposes that are associated with the land cover (e.g. raising cattle, recreation, or urban living), (Meyer and Turner eds. 1994) and relates to human activities on the land. A single category of land use may be associated with a variety of land covers. Similarly, a single land cover may support multiple uses. For example, residential land use may have tree cover, grass cover, road cover, and roof cover while a forest may be used for timber production, recreation, or wildlife perservation (Lillesand and Kiefer 1996).

Land use change may involve either a shift to a different use, such as agricultural land changing to residential, or an intensification of the existing use, such as from light to heavy industry.

The dual role of human activity in contributing to the causes and experiencing the effects of global change processes brought about by land use changes emphasizes the need for better understanding of the interaction between humans and the environment. This need becomes more imperative as changes in land use become more rapid. (source: http://www.ciesin.org/TG/LU/overview.html)

The Land Use/Water Relationship

The relationship between land use and water qualityand water quantity is bidirectional. Land use activities have direct impacts on water resources, while water quality and quantity greatly influence the siting of land use activities. Land use is in part determined by environmental factors such as soil characteristics, climate, topography, and vegetation. To manage land, a better understanding is needed between land use/land cover and water resources.