Water resources management under possible future climate and land use changes: The application of the Integrated Hydrological Modelling System, IHMS

The Integrated Hydrological Modelling System, IHMS, has been developed to study the impact of climate and land use changes on water resources. The system comprises three models: the distributed catchment scale model DiCaSM, which deals with the unsaturated zone; the MODFLOW model, for saturated zone and groundwater flow; and the SWI model, for seawater intrusion in coastal areas. These models can be applied either together or separately. Four sites were considered in this study. In the first site, the DiCaSM application on Candelaro catchment in the Apulia region, Italy, proved the ability of the DiCaSM to successfully simulate the stream flows (2001–2002). When applying the possible future climate change scenarios for southern Italy as reduced winter rainfall by 5–10 %, reduced summer rainfall by 15–20 %, winter temperature rise by 1.25–1.5 °C and summer temperature rise by 1.5–1.75 °C, the results indicated that, by 2050, the groundwater recharge in the Candelaro catchment would decrease by 21–31 % and the stream flows by 16–23 %. The model’s results also showed that the projected durum wheat yield up to 2050 is likely to decrease between 2.2 and 10.4 % due to the reduction in rainfall and the increase in temperature. The results also indicated that, by 2050, the harvest date for this crop would be between 10 and 14 days earlier than at present due to the increase in temperature leading to early maturity of the crop and early harvesting. In the second site, the DiCaSM model has been applied on Mimoso catchment in the Brazilian North East region. The model successfully simulated stream flows (2000–2008) and soil moisture (2004–2007). Based on a range of climate change scenarios for the region, the DiCaSM model forecasted a reduction of 35, 68 and 77 %, in groundwater recharge, and of 34, 65 and 72 % (average of high- and low-emission scenarios) in stream flow for the time spans 2010–2039, 2040–2069 and 2070–2099, respectively. These reductions would produce severe impact on water availability in the region. Introducing castor beans as a biofuel crop to the catchment would increase the groundwater recharge and stream flow, mainly if the caatinga areas (forests) would be converted into castor beans production. Changing an area of 1,000 ha from caatinga to castor beans would increase the groundwater recharge by 46 % and the stream flow by 3 %. If the same area of pasture is converted into castor beans, there would be an increase of groundwater recharge and stream flow by 24 and 5 %, respectively. Such results are expected to impact on environmental policies for the Brazilian Northeast and to the biofuel production perspectives in the region. In the third site, DiCaSM model was applied on a second catchment in North East Brazil, Tapacurá catchment. The model successfully simulated stream flow (1970, 2000, 2004 and 2005) and the soil moisture (2004–2007). When applying the possible future climate change (low-emission scenario B1) scenarios on the catchment, the results indicated a possible reduction in water availability by #13.9, #22.63 and #32.91 % in groundwater recharge and by #4.98, #14.28 and #20.58 % in surface flows for the time spans 2010–2039, 2040–2069 and 2070–2099, respectively. Changing the land use by reforestation of part of the catchment area, i.e. replacing current use of arable land, would decrease groundwater recharge by #4.2 % and stream flow by #2.7 %. Changing land use from vegetables to sugarcane would result in decreasing groundwater recharge by around #11 % and increasing stream flow by 5 %. In the fourth site, the IHMS was applied on the Kouris and Akrotiri catchments in Cyprus. DiCaSM and MODFLOW models were applied. The system was successfully tested against the stream flow (1990–1997) and groundwater levels (2000). When applying the possible future climate change scenarios, the model showed that, by 2050, the amount of groundwater and surface water would decrease by 35 and 24 % for Kouris and 20 and 17 % for Akrotiri, respectively. The four catchments represented a wide range of environmental conditions and land use. The results of possible climate and land use changes showed that these changes would have great impact on water resources availability. These results are useful for planners, water authorities and policy makers to balance the current and future supply and demand. In that respect, the Integrated Hydrological Modelling System, IHMS, could be used as a reliable water resources management tool.