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An Ecohydrologic Model for a Shallow Groundwater Urban Environment
Arden, S., Cissy Ma, AND M. Brown. An Ecohydrologic Model for a Shallow Groundwater Urban Environment. WATER SCIENCE AND TECHNOLOGY. IWA Publishing, London, Uk, 70(11):1789-1797, (2014).
Complex water issues cannot be solved by a traditional “siloed” water management approach. In a water-connected world, sustainable solutions require a system-based approach. This study is one of a series of investigations that provide necessary understandings of the interactions of natural systems and built infrastructure. Particularly, it addresses the question how the urbanization factors like soil, vegetation cover, water table, impervious surface affects the evapotranspiration. It also provides an important missing link in local hydrological cycle. These understandings have potential implications for holistic urban water system management.
The urban environment is a patchwork of natural and artificial surfaces that results in complex interactions with and impacts to natural hydrologic cycles. Evapotranspiration (ET) is a major hydrologic flow that is often altered from urbanization, though the mechanisms of change are sometimes difficult to tease out. This paper uses a plot-scale model under idealized conditions to test the effects that soil, vegetation cover, groundwater table, microclimates, and impervious surface have on ET. Through this simplified approach, a better idea of the degree to which specific variables control ET at the plot scale is assessed. It was found that: loamy soils can sustain vegetation transpiration more than sandy soils; mature tree covers with deep root structures have higher annual ET rates than shallow rooted covers such as grass; shallow groundwater tables reduce the differences in annual ET fluxes between different vegetation covers; the increase in ambient temperature resulting from the urban heat island effect will increase local vegetative transpiration so long as soil moisture is available, and reductions in annual ET at the watershed scale from increases in impervious surfaces may be mitigated through elimination of DCIA at the plot-scale. These understandings have potential implications for holistic urban water system management.