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

Abstract

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.

Growing ‘Smart’? Urbanization Processes in the Pune Urban Agglomeration

“…A reasonable performance of the model is indicated through various indices (e.g., Nash-Sutcliff efficiencies of 0.68 and 0.67, percentage bias of +4% and +24% for two different gauges, respectively). The model was used to (i) analyse the impacts of land use changes between 1989 and 2009 on the water resources [10], to (ii) analyse the impact of climate change on the water resources based on downscaled future climate projections up to the year 2079 [14], and to (iii) analyse the impacts of possible future land use and climate change on the water resources using land use projections from the model SLEUTH [15,16] in combination with the downscaled climate projections.…”

“…Urban expansion metrics (e.g., expansion contribution rate, expansion percentage of change, annual expansion rate) were calculated for each administrative unit in the Pune metropolis and used to explain the temporal dynamics of urbanization of each individual spatial unit [18]. SLEUTH was also used to model land use change in the Mula and Mutha watershed and thus to assess the impact of land use change outside of the urban area [16]. The integration of the land use change model allows to address the combined impact of future land use and climate change.…”

“…An assessment of land use changes between 1989 and 2009 shows that agricultural areas increased (+4%), leading to an increased irrigation water demand [10] (Figure 3). Future land use model predictions until 2028 indicate that the ongoing urbanization (+8%) leads to a decrease of agricultural areas (−4%) [16], whereas in the past the loss of agricultural land due to urbanization was compensated by a relocation of agriculture to more remote areas in the catchment [10]. However, this might not necessarily result in a lower irrigation demand in the future, as the loss of agricultural area might be compensated by an intensification of management practices on the remaining agricultural fields.…”

“…Moreover, an assessment of future climate change impacts indicates that the storage capacity of the reservoirs is more frequently not met during the rainy season [14]. In addition, extreme dry years can aggravate the effects of land use change on water resources in the future [16]. Therefore, climate change and land use change may further exacerbate the competition for the limited water resources in the catchment.…”

Performance Evaluation of SWAT Model for Land Use and Land Cover Changes under different Climatic Conditions: A Review

“…Even though more sophisticated methodologies to describe land use change conditions by using land use change models are available, these are rarely dynamically incorporated with hydrologic impact assessments. Land use change scenarios may be derived as a result of simple assumptions [72][73][74]. Therefore, they provide a basis to predict land use change in a more complex technique.…”