Hydrological model with runoff-evaporation processes

Plethoric hydrological models have been developed for RGA where rainfall-runoff processes are dominating, and runoff generating processes are emphasized as mentioned before. Runoff absorbing processes such as water system dispersion, depression storage, and irrigation abstraction etc. are not integrated in this kind of runoff generating models. Some modeling approaches for river basin management take account of only human abstracting water such as irrigation water consumption (Dunn and Ferrier, 1999; Li et al., 2004). However, the models do not attempt to model the natural runoff absorbing processes and represent the ecosystem role in runoff-evaporation processes. Thus, the existing ranges of hydrological models are limited in the ability to integrate both runoff generating and absorbing processes.

Natural runoff absorbing processes occur when accumulated runoff is dispersed because of natural hydraulic head difference. Such as the flow from channel to the aquifer, which occurs widely in arid environments, is an important component of natural runoff absorbing processes. More obvious runoff absorbing processes are related to human activities, e.g. river water is diverted into irrigation channels and consumed among the fields. In a sense, water resources management is the way for human trying to influence and manage runoff-evaporation processes. In the human dominated earth's ecosystem, Humanity now uses about quarter of the total terrestrial evapotranspiration and more than half of the runoff that is geographically and temporally accessible (Postel et al., 1996). Major rivers, including the Colorado, the Nile, and the Ganges, are used so extensively that little water reaches the sea (Vitousek et al., 1997). Humanity impacted runoff-evaporation processes even induce river flow cutoff in some semi-arid river basin, e.g. the Yellow river. Hydrological model with respect to runoff-evaporation processes is highly urged to represent the hydrological cycle characteristics with human impact.