Integrated modeling of global change impacts on land and water resources.

There is a common scientific understanding that global change impact analysis, mitigation, and adaptation require interdisciplinary work. Integrated modeling could help to address the challenges associated with the impacts of global change. Particularly, integrated modeling that takes feedback effects into account will allow for the derivation of climate resilient land use and land management. Here, we call for more of such integrated modeling work focusing on the interdisciplinary subject of water resources and land management. As a proof-of-concept, we tightly couple a hydrologic (SWAT) and a land use model (CLUE-s) and illustrate the benefits of this coupled land and water modeling framework (LaWaCoMo) with a scenario on cropland abandonment induced by water stress. As compared to standalone model runs of SWAT and CLUE-s for the past, LaWaCoMo performs slightly better regarding measured river discharge (PBIAS: +0.8% and +1.5% compared at two gauges) and land use change (figure of merit: +6.4% and +2.3% compared to land use maps at two points in time). We show that LaWaCoMo is suitable for global change impact analysis as it is sensitive to climate and land use inputs as well as to management decisions. Our results shed light on the importance of feedback effects between land use and hydrology to assess impacts of global change on land and water resources accurately and consistently. To facilitate that the developed methodology can serve as a blueprint for integrated modeling of global change impacts, we used two freely available models that belong to the most widely used models in their respective disciplines.

Dynamic integration of land use changes in a hydrologic assessment of a rapidly developing Indian catchment.

Rapid land use and land-cover changes strongly affect water resources. Particularly in regions that experience seasonal water scarcity, land use scenario assessments provide a valuable basis for the evaluation of possible future water shortages. The objective of this study is to dynamically integrate land use model projections with a hydrologic model to analyze potential future impacts of land use change on the water resources of a rapidly developing catchment upstream of Pune, India. For the first time projections from the urban growth and land use change model SLEUTH are employed as a dynamic input to the hydrologic model SWAT. By this means, impacts of land use changes on the water balance components are assessed for the near future (2009-2028) employing four different climate conditions (baseline, IPCC A1B, dry, wet). The land use change modeling results in an increase of urban area by +23.1% at the fringes of Pune and by +12.2% in the upper catchment, whereas agricultural land (-14.0% and -0.3%, respectively) and semi-natural area (-9.1% and -11.9%, respectively) decrease between 2009 and 2028. Under baseline climate conditions, these land use changes induce seasonal changes in the water balance components. Water yield particularly increases at the onset of monsoon (up to +11.0mm per month) due to increased impervious area, whereas evapotranspiration decreases in the dry season (up to -15.1mm per month) as a result of the loss of irrigated agricultural area. As the projections are made for the near future (2009-2028) land use change impacts are similar under IPCC A1B climate conditions. Only if more extreme dry years occur, an exacerbation of the land use change impacts can be expected. Particularly in rapidly changing environments an implementation of both dynamic land use change and climate change seems favorable to assess seasonal and gradual changes in the water balance.