Exploring Water Management Options with COWA: A Coupled Human-Climate-Water Model

Water is, and has always been, a critical resource for survival of civilizations and a key to prosperity of societies. Over the past several decades, demand for freshwater has increased significantly due to growth of both population and consumption. Such soaring demands have put serious strain on freshwater sources at many regions of the world, and climate change can only worsen the uncertainty in availability of needed freshwater. Therefore, it is essential to study the water system in conjunction with the Earth system and the Human system. Most importantly, we need to understand effectiveness of various managerial decisions on the water system, since efficient policy making is the only viable solution for sustaining water sources and supply (reservoir) at any water-scarce region of the world.

We have developed a COupled WAter model (COWA) that is integrated with the human system and the earth system through bidirectional feedbacks. Policies are introduced as drivers of the model so that the effect of policies on the system can be measured as we change each policy knob. We have applied our model to a data-rich watershed in the United States: Phoenix AMA watershed which is rather dry. Model is trained with the data from 1900-2010, and then projections are made for the next several decades. Historical data were recovered from the records at the US National Archives. We have also used remotely sensed satellite data in conjunction with data from local municipalities. Response of the system to six different short and long term policies are presented under three different climate scenarios. We show that it is possible to guarantee the freshwater supply and sustain the freshwater sources through a proper set of policy choices.