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Assessing Groundwater Irrigation Sustainability in the Euro-Mediterranean Region with an Integrated Agro-Hydrologic Model

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Assessing Groundwater Irrigation Sustainability in the Euro-Mediterranean Region with an Integrated Agro-Hydrologic Model 19th EMS Annual Meeting: European Conference for Applied Meteorology and Climatology 2019 Adv. Sci. Res., 17, 227–253, 2020 https://doi.org/10.5194/asr-17-227-2020 © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License. Assessing groundwater irrigation sustainability in the Euro-Mediterranean region with an integrated agro-hydrologic model Emiliano Gelati1,a, Zuzanna Zajac1, Andrej Ceglar1, Simona Bassu1, Bernard Bisselink1, Marko Adamovic1, Jeroen Bernhard2, Anna Malagó1, Marco Pastori1, Fayçal Bouraoui1, and Ad de Roo1,2 1European Commission, Joint Research Centre (JRC), Ispra, Italy 2Department of Physical Geography, Utrecht University, Utrecht, the Netherlands anow at: Department of Geosciences, University of Oslo, Oslo, Norway Correspondence: Emiliano Gelati ([email protected]) Received: 16 February 2020 – Revised: 27 July 2020 – Accepted: 21 September 2020 – Published: 31 October 2020 Abstract. We assess the sustainability of groundwater irrigation in the Euro-Mediterranean region. After analysing the available data on groundwater irrigation, we identify areas where irrigation causes groundwater depletion. To prevent the latter, we experiment with guidelines to restrict groundwater irrigation to sustainable levels, simulating beneficial and detrimental impacts in terms of improved environmental flow conditions and crop yield losses. To carry out these analyses, we apply the integrated model of water resources, irrigation and crop production LISFLOOD-EPIC. Crop growth is simulated accounting for atmospheric conditions and abiotic stress factors, including transpiration deficit. Four irrigation methods are modelled: drip, sprinkler, and intermit- tent and permanent flooding. Hydrologic and agricultural modules are dynamically coupled at the daily time scale through soil moisture, plant water uptake, and irrigation water abstraction and application. Water abstractions of other sectors are simulated based on requirement data. Water may be withdrawn from groundwater, rivers, lakes and reservoirs. As groundwater is abstracted to buffer the effects of drought, we use groundwater deple- tion to detect unsustainable water exploitation. We characterise reported data of annual groundwater abstractions for irrigation available at country and sub-national levels. Country data are the most complete, but their spatial resolution is often coarse. While the resolution of sub-national data is finer, their coverage is heterogeneous. Simulated and reported irrigation groundwater abstractions compare well in several areas, particularly in France, while some structural discrepancies emerge: simulated values tend to be larger than those reported, especially in southern Spain; and simulated inter-annual variability is significantly smaller than reported in some areas, most remarkably in Turkey. Potential causes of these discrepancies are simplified model assumptions influenc- ing irrigation frequency and amounts; lack of high temporal and spatial resolution data on irrigated areas, and irrigation technologies and distribution; and possible unreported abstractions in areas where groundwater irriga- tion is significant. We identify areas undergoing groundwater depletion from model simulations. In the southern Iberian Peninsula, Greece, Middle East and northern Africa, most simulated depletion is caused by irrigation. In other Mediterranean areas, depletion is caused by all sectors combined. From well measurements of groundwa- ter table depth in Spain, we find statistically significant decline rates affecting large areas of the south, thus in agreement with the model, but also areas in the north-eastern and central parts where model estimates detect no depletion. The comparison of model- and well-based depletion rates is limited by spatial scale differences and groundwater model assumptions, for which we suggest potential research directions. We design rules restricting irrigation groundwater abstraction to prevent groundwater depletion and minimise severe irrigation shortages. We optimise them and simulate their effects in the southern Iberian Peninsula. Irrigation restrictions cause crop yield reductions in groundwater-dependent irrigated areas, particularly in the Algarve and Segura river basin dis- tricts. At the same time, they positively impact environmental flows. This study shows the potential of integrated Published by Copernicus Publications. 228 E. Gelati et al.: Euro-Mediterranean groundwater irrigation agro-hydrologic modelling for detecting water resources over-exploitation and exploring trade-offs between crop production, sustainable irrigation and ecosystem support. 1 Introduction tion in the long term, potentially threatening future food security (Seckler et al., 1999; Moench et al., 2003; Gior- Freshwater availability is put under increasing pressure by dano, 2009; Garduño and Foster, 2010; Brown, 2012). More- global warming, land use changes, and water abstractions over, groundwater depletion may trigger intertwined posi- (IPCC, 2019). Large alterations of continental water storages tive feedback mechanisms that reduce freshwater availabil- and flows already occur in (semi-)arid regions where irriga- ity even further: decrease of streamflow, reduction in cap- tion is the main water use (Döll et al., 2009, 2012, 2016; illary rise from groundwater and therefore in soil moisture, Siebert et al., 2010; Famiglietti, 2014; Long et al., 2017). loss of springs and wetlands, ecosystem damage, land sub- Changes in the water cycle, increasing food demand, soil sidence, sea level rise, and salt-water intrusion in coastal degradation, and the use of agricultural land for urban de- aquifers (Levine and Salvucci, 1999; Llamas and Custodio, velopment and bio-fuel production pose the challenge of 2002; Konikow and Kendy, 2005; Pokhrel et al., 2012; Glee- adapting agriculture to achieve food security within planetary son and Richter, 2018; Rodell et al., 2018; de Graaf et al., boundaries, among which water limitation is crucial (Rock- 2019). At the same time, projected growth in population, ström et al., 2009; Rockström and Karlberg, 2010; Falken- economy, agricultural land use, and drought intensity and fre- mark, 2013; Elliott et al., 2014; Hunter et al., 2017). There- quency may increase groundwater demand even further (Tay- fore, we investigate here to which extent irrigation can be lor et al., 2012). sustainably applied, and which crop production levels can be In the Euro-Mediterranean region, global warming is pro- achieved under sustainable water abstraction conditions. gressively increasing frequency, intensity, duration and ex- Irrigation accounts for 70 % of water withdrawals and tent of droughts (Planton et al., 2012; Lehner et al., 2017; 90 % of consumptive water use globally (Shiklomanov, Samaniego et al., 2018; Bisselink et al., 2018b). The Mediter- 2000; Molden et al., 2007; IAASTD, 2009). These figures ranean basin has been identified as a “climate change hot reflect the growth of irrigated agriculture during the XX cen- spot”, with projected drier summer seasons due to the in- tury: areas equipped for irrigation have more than quadru- creasing gap between potential evapotranspiration and pre- pled (Siebert et al., 2015), while irrigation water use has cipitation (Giorgi, 2006; Greve et al., 2018). This drying more than doubled (IPCC, 2019). In the future, freshwater trend is likely to be worsened by ecosystem degradation allocation to agriculture may be further constrained by the caused by human land management (Guiot and Cramer, compounding effects of global warming and increasing re- 2016). According to AQUASTAT data (FAO, 2020), agricul- quirements by other sectors (Haddeland et al., 2006; Hadde- ture accounts for over 60 % of water withdrawals in several land et al., 2014; Molden et al., 2007; Rosegrant et al., 2009; Mediterranean countries (Algeria, Cyprus, Egypt, Greece, Chartres and Sood, 2013). However, unsustainable ground- Iraq, Israel, Libya, Morocco, Portugal, Spain, Syria, Tunisia, water abstraction for irrigation – including the mining of Turkey). Regional adaptation of irrigated agriculture and wa- fossil aquifers – is already taking place in several regions, ter management may become necessary in light of the pro- leading to long-term water storage depletions (Konikow and jected water scarcity increases (García-Ruiz et al., 2011; Kendy, 2005; Scanlon et al., 2007; Siebert et al., 2010; Wada Daccache et al., 2014; Fader et al., 2016; Malek and Verburg, et al., 2012; Dalin et al., 2019). Groundwater has been in- 2017). creasingly used to expand irrigated agriculture, especially Climate change and growth of human activities are inter- since the 1970s decline in the availability of sites for build- linked challenges to water and food systems, whose secu- ing new dams, which had been the main source of irrigation rity will require improving water resources management and development until then (Brown, 2012). In 2010, Siebert et al. allocation (Rodell et al., 2018). Design of adequate actions estimated that 43 % of global consumptive water use for irri- should be informed by integrated models that can represent gation was drawn from groundwater. the dynamic interactions between climate, water resources Groundwater is used to buffer drought impacts in and human activities, including crop growth (Gleeson et al., (semi-)arid regions, due to its generally larger reliability and 2012; Dalin et al., 2019). availability compared to surface water (Garrido et al., 2006; Reported statistics
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