HUMAN-HYDROLOGY INTERACTIONS IN THE URBANIZING ARID WEST

Human behavior underlies many changes in hydrologic systems of the arid west. Yet the underlying reasons that cause people to affect hydrologic systems have only received limited exploration by the hydrologic community. The nature of human-hydrology interactions has evolved as the Wasatch Front settlers of 150 years ago captured surface water with buckets, used small irrigation systems and discharged only minor amounts of waste to surface water. Urban growth has led to complex systems for capturing water with dams and wells, transferring water between watersheds, discharging wastewater and allocating water rights. The boundary of the urban land area has grown while urban activity has impacted agriculture, forestry and recreation activity in the surrounding watersheds. These complex interacting systems involve human-related feedbacks and delays that must be considered as hydrologists attempt to discern the causes of observed changes in fluxes, pathways and stores of water and solutes. Human behavior and socio-economic trends must be studied to anticipate how human decision-making might affect hydrologic systems. For example, converting agricultural land to urban use changes the timing, magnitude and chemistry of water flowing through the system from a seasonal agricultural supply/discharge pattern to a more continuous urban pattern. Although agricultural land may be taken out of production in response to economic considerations, the strong tradition of farming families has led many agriculturalists to support uneconomic farms by working in off-the-farm jobs. Thus, personal choice, access to non-farming jobs, water rights status and the hardship of longterm drought play key roles in determining whether commercial farmland will be sold for urban development and hobby farms. As land is taken out of production, and water is conserved by farmers and urban residents, the downstream hydrologic system can be modified in unanticipated ways. These issues suggest questions that can be explored with a systems thinking approach: (1) how might past watershed modifications compromise our ability to adapt to climate change, (2) how might the personal/policy decisions involved in reducing urban sprawl impact western watersheds, and (3) how might changes in water rights legislation affect watershed processes?