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Modelling water demand and availability scenarios for current and future land use and climate in the Sava River Basin
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Modelling water demand and availability scenarios for current and future land use and climate in the Sava River Basin

Addressing the water-food-energy-ecosystem nexus

Modelling water demand and availability scenarios for current and future land use and climate in the Sava River Basin

Addressing the water-food-energy-ecosystem nexus

Väljaande metaandmed

The impact of various combinations of land use change, climate change and policy measures on the water-energy-food-environment nexus in the Sava river basin has been evaluated through 170 simulations with the LISFLOOD water resources model for 30- year periods. The LISFLOOD model was first calibrated and validated for the Sava basin against weather and river discharge observations, which were partially obtained from the International Sava River Basin Commission. The goodness-of-fit score obtained for the most downstream station for the calibration period was 0.91, suggesting that the model performance was excellent overall. Also, it was found that the model performance was relatively consistent amongst sub-catchments of the Sava river basin. For the Sava river basin, we found in this study that more intense irrigated agriculture does have the potential to increase crop yields considerably, but available water resources are not sufficient to realise this. Also, if irrigation would be increased drastically, other sectors would be negatively influenced, such as the energy sector (reduced cooling water availability, potentially less water at times produce hydropower), navigation (more frequent and lower low-flows), and the environment (breaches of environmental or minimum flow conditions). With respect to most of the water resources indicators, the projected land use changes until 2050 balance each other out, and the net effect is only marginal. Land use projections for Slovenia until 2050 show a substantial increase of forested area at the expense of arable land and semi-natural vegetation. Urban land use is expected to increase by roughly 22% as compared to present day; industrial land use is expected to increase by roughly 27%. For Croatia, forest areas are expected to increase substantially between 2010 and 2050 until 50% of the country’s land surface is forested. Areas of arable land and semi-natural vegetation are expected to decrease substantially. Industrial and urban land uses are expected to increase by respectively 22% and 1%. Effects on water resources would be more significant with increased irrigation to increase the crop yield of e.g maize. This would lead to an increase in water demand from 2216 Mm3/year to 3337 Mm3/year. Overall water demand in the Sava basin would further increase to around 6000 Mm3/year if we combine both increased irrigation and climate projections until 2100. The average simulated maize yield could increase from 5.7 tons/ha at present conditions to 9.9 tons/ha in case of increased and optimum irrigation. These substantial increases in irrigation, which would lead to substantial crop yield increases as well, would lead to water scarcity in parts of the Sava basin. Also, there just is not sufficient water to irrigate all areas which are water-limited for crop growth. Existing irrigation plans and irrigating the areas which were previously equipped for irrigation (according to FAO) seems more feasible from a water resources perspective. Flood peaks are projected to remain unchanged as a consequence of projected land use changes until 2050 for the Sava basin. However, with climate change projections we do simulate an overall increase in the flood peaks with 13% for the 2011-2040 period and a 23% increase for the 2071-2100 period. River low-flows decrease moderately for the 2011-2040 scenarios. For the end of the century 2071-2100, lowflow values are projected to moderately increase as compared to the control 1981-2010 climate. Excessive irrigation would result in a severe decrease of the lowflow discharges with 50-60%. As for ecological flows, similar observations can be made. Navigation in the main Sava river may be affected by these trends. Water availability for energy production - hydropower and cooling water for thermal and nuclear power stations – is projected to decrease by an average of 3.3% for 2030 under RCP4.5, whereas RCP8.5 would result in a 1.3% increase. End of the century simulations yield a 17.6% higher Q50 for RCP4.5 and 23.1% higher for RCP8.5. Excessive irrigation could affect the water availability for power production, especially for cooling thermal power stations. Hydropower reservoirs could be turned into multi-functional reservoirs, also serving downstream irrigation needs and flood control, and thus serve multiple purposes. Soil water stress conditions, which would potentially reduce agricultural crop yields, are especially affecting the lower parts of Bosnia-Herzegovina, Croatia and Serbia under current climate. Climate impact simulations show an increase of soil water stress of 9% for 2030. For the end of the century, RCP4.5 shows a 1% increase, whereas RCP8.5 shows a 7% increase in soil water stress. This might indicate stronger needs for irrigation in the future to maintain current crop yields. Our climate impact simulations show a moderate decrease of groundwater resources for Slovenia and the higher parts of Croatia and Bosnia Herzegovina until 2030. For the end of the century runs we observe increases in groundwater resources. Increased irrigation practices would seriously reduce groundwater resources again. Also, if relatively more groundwater is used for irrigation replacing surface water, groundwater resources decrease as well. Feedback of Sava River Basin Commission experts has been taken into account and the suggested improvements will be used in the forthcoming Danube Water Nexus report.
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ISSN 1831-9424
ISBN 978-92-79-54586-3
DOI 10.2788/52758
Katalooginumber LB-NA-27-701-EN-N
ISSN 1018-5593
ISBN 978-92-79-54585-6
DOI 10.2788/789075
Katalooginumber LB-NA-27-701-EN-C
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ISSN 1831-9424 ISBN 978-92-79-54586-3 DOI 10.2788/52758 Katalooginumber LB-NA-27-701-EN-N
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ISSN 1018-5593 ISBN 978-92-79-54585-6 DOI 10.2788/789075 Katalooginumber LB-NA-27-701-EN-C
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