Land-use Change May Worsen Water Availability and Quality

Using numerical models, researchers at USGS EROS and its contractors ARTS and ERT have projected land-cover changes to the middle of this century for the Cedar River Basin in the Midwestern US, in an effort to predict how water quantity and quality in this part of the world might evolve in future

The analyses indicate that in this basin, urban areas and pasturelands for cultivating biofuel crops may significantly increase in size while rangelands might decrease in size. Hydrological and water-quality modelling results have also highlighted several potential adverse consequences under these projected land-cover changes, such as flooding and drought – regardless of future climate change – together with impaired water quality due to the development of biofuels.

"Increases in population and improvements in global living standards are expected to result in expanded urban areas and an increased demand for agricultural commodities," said study lead author Yiping Wu, a scientist at ASRC Research and Technology Solutions. "Increased demand for biofuels may also cause changes in land-use and management practices such as converting grass – or marginal – lands to ones that can be used to cultivate bioenergy crops."

Wu and colleagues Shuguang Liu, Terry Sohl and Claudia Young projected land-cover changes in the Cedar River Basin to 2050 using the FORE-SCE land-cover model under the IPCC A1B scenario. This scenario is characterised by moderate population growth, rapid technological development, significantly greater energy demands and changes in global living standards. They also investigated the potential environmental impacts of land-cover changes, focusing on the water cycle and water quality using a well-established hydrological and water-quality model (SWAT).

The authors compared the baseline land cover (NLCD 2001) with the projection for 2050 to diagnose land-cover changes. The analyses show that croplands could remain nearly unchanged in this highly agricultural area. In contrast, however, pasturelands and urban areas would increase by about 81% and 68%, respectively, accompanied by a decrease of 62% in rangelands.

These important land-cover changes, especially the substantial increase in impervious areas caused by urban expansion, may have significant impacts on the hydrological cycle of the basin. The researchers are concerned that there might be an increase in surface run-off (overland flow) and a reduced amount of water infiltration based on physical hydrological simulations. Increased surface run-off can lead to higher peak streamflow, which may intensify the risk of flooding, while reduced infiltration could decrease the amount of water in the soil and baseflow. As a major contributor to the dry-season streamflow, decreased baseflow can result in less stream water and both flooding and drought would reduce the quantity of water available.

Source: Environmental Research

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