Agricultural Irrigation Water Use in a Closed Basin and the Impacts on Water Productivity: The Case of the Guadalquivir River Basin (Southern Spain)

water Article Agricultural Irrigation Water Use in a Closed Basin and the Impacts on Water Productivity: The Case of the Guadalquivir River Basin (Southern Spain) Alfonso Expósito 1,* and Julio Berbel 2 1Department of Economic Analysis, University of Sevilla, 41018 Sevilla, Spain 2Department of Agricultural Economics, University of Cordoba, 14014 Cordoba, Spain; [email protected] *Correspondence: [email protected]; Tel.: +34-656-626953 Academic Editor: Davide Viaggi Received: 15 November 2016; Accepted: 13 February 2017; Published: 20 February 2017 Abstract: This paper analyses the agricultural irrigation water use in a closed basin and the impacts on water productivity, and examines how they have affected the ‘closure’ process of the Guadalquivir river basin observed in recent decades. Following a period of expansion in irrigation, an administrative moratorium was declared on new irrigated areas in 2005. Since then, the main policy measure has been aimed at the modernisation of irrigated agriculture and the implementation of water conservation technologies. The analysis carried out in this paper shows a significant increase in mean irrigation water productivity in the pre-moratorium period (1989–2005), driven by the creation of new irrigated areas devoted to high value crops and with a dominant use of deficit irrigation strategies, while a second phase (2005–2012) is characterised by slower growth in terms of the mean productivity of irrigation water, primarily as a result of a significant reduction in water use per area. Findings show that productivity gains seem to have reached a ceiling in this river basin, since technological innovations (such as new crops, deficit irrigation, and water-saving and conservation technologies) have reached the limits of their capacity to create new value. Keywords: irrigation water productivity; agricultural water use; basin closure; water policy 1. Introduction Irrigated agriculture occupies about 15% of the total cultivated area in Spain but is responsible for 60% of the total value of agricultural production; the average production per hectare of irrigated crops is 6.5 times greater than that of rain-fed agriculture. Irrigation plays a more important role in southern Spain, where the Guadalquivir river basin (RB) is located; this basin is subject to typical Mediterranean intra- and inter-seasonal rainfall variability and increasing pressures on scarce water resources. The Guadalquivir RB, which is representative of Mediterranean agriculture, has undergone intense transformation in the last 50 years, characterised by a significant growth of irrigated areas, a progressive change in the composition of crops and widespread implementation of water-saving and conservation technologies (WCTs). Farmers must adapt to water scarcity and a continued decline in farm incomes (falling 1.1% annually since the beginning of the 90s, according to Spanish Ministry of Agriculture and Environment (MARM) [ 1 ], which attributes this decrease to the increasing cost of inputs and lower commodity prices), and they have reacted by prioritising crops with greater value added per hectare and higher productivity per water input. Moreover, farmers facing growing resource scarcity and increasing water costs have responded by using the resource more efficiently; consequently, significant investments (public and private) have been made over the last decades to improve water-use efficiency as part of an initiative to modernise irrigated areas in southern Spain. Water 2017,9, 136; doi:10.3390/w9020136 www.mdpi.com/journal/water Water 2017,9, 136 2 of 15 The aim of this paper is to analyse the changes in agricultural water use patterns, the irrigation modernisation process, and the impacts on irrigation water productivity, which have characterised the ‘closure’ process of the Guadalquivir RB observed in recent decades. Basin closure is an anthropogenic process and is manifested at societal as well as ecosystem levels [ 2 ]. The main changes observed in the Guadalquivir RB in recent decades have been (1) significant growth in the demand for irrigation water (2) increasing economic productivity associated with water, and (3) intense process of modernisation of irrigation techniques (WCTs) used in the basin. To this end, the rest of this paper is organised as follows. The next section introduces the theoretical framework regarding mature water economies and basin closure. The third section briefly describes the main changes that have taken place in Guadalquivir basin with respect to: (a) the extent of the irrigated area; (b) water consumption; and (c) modernisation of irrigation schemes. It also examines the effects of these changes in the basin over the last two decades. The fourth section outlines the model for understanding the process of basin closure, a process characterised by growing pressures on water resources mainly linked to agricultural water demand in a context of water scarcity, and the consequences of increasing economic productivity of irrigation water. A brief discussion of the findings is offered in the fifth section, and the paper ends with some concluding remarks. 2. Mature Water Economies and Basin Closure According to Randall [ 3 ], in the 1980s the Australian water economy entered a ‘mature phase’ characterised by: (1) inelastic water supply with increasing marginal supply costs (aquifers were already heavily exploited, the best dam locations had been taken and other rivers were protected); (2) high and growing demand (with increasing conflicts among water users); (3) an aging infrastructure which required expensive renovation; (4) a context of increasing negative externalities and (5) a rising social cost of subsidising water use. Randall’s framework for describing the mature phase of a water economy has been applied to other countries, such as Spain, where the radical new ‘Water Law’ was approved in 1985. This law reinforced the public nature of all water resources, ensuring that they are used according to prior allocation of water rights, and Randall’s description of the situation in Australia played a key role in the ideological debate surrounding the related Spanish legislation. Randall’s analysis was developed in the field of public policy and agricultural and environmental economics; accordingly, his framework is often used in this field. The level of analysis therefore focuses on national policy and the instruments recommended are mainly economic in nature (i.e., water pricing or markets). A different approach comes from the fields of hydrology and agronomy, where the concept of ‘basin closure’ has been widely used since a 2006 seminar organised by the Stockholm International Water Institute (SIWI) and the Consultative Group on International Agricultural Research (CGIAR), held to discuss the issue of closed basins. In this seminar, the symptoms of a river basin closure and its social and ecological impacts were analysed, as well as the necessary adaptation processes required to achieve a ‘soft landing’. Evidence of basin overbuilding and basin closure can be found in many basins, including those of the Jordan River, the Krishna River, the Lerma–Chapala River, the Murray–Darling River, the Colorado River, the Indus River in India and Pakistan, the Yellow River and many others. In this regard, basin closure is defined as an anthropogenic process and the term has been used to describe the situation in a number of basins and aquifers [ 2 ]. An example of this analytical framework can be found in Comair et al. [ 4 ] and Venot et al. [ 5 ], which describe how population growth and increased agricultural demand are contributing to the closure of the Jordan basin. To the best of our knowledge, the concepts of ‘mature water economy’ and ‘basin closure’ have not been fully integrated in the existing literature and they are rarely included together in the same study. An explanation for this may lie in the different levels of analysis of the two analytical frameworks. Randall’s ‘mature water phase’ is defined at national level, with economic and normative instruments defined at this level. Conversely, basin closure is defined in hydrological terms, and economic Water 2017,9, 136 3 of 15 instruments may be used when the basin belongs mainly to a single country. Nevertheless, as most of the basins listed above are international, finding sustainable solutions entails greater complexity. We argue that Randall’s ‘mature phase’, which is characterised by inelastic water supply with increasing marginal costs, eventually reaches a point where resource supply augmentation is no longer feasible and the inelastic water supply becomes vertical. Thus, the question arises as to how to allocate scarce resources in a basin or aquifer that is already ‘overallocated’. Overallocation is a common problem in water-scarce regions. A recent study by Grantham and Viers [ 6 ] estimates that overall allocation of water resources in California is five times the average supply of renewable water resources, with some rivers reaching overallocation levels of up to 1000%. We believe that the framework of a mature water economy phase is complementary to the hydrological and ecosystem concept of a ‘closed basin’, as the solutions to this problem should consider the local situation (natural, social and technical constraints at aquifer or subbasin level), as well as the national policy institutions (the legal framework for managing water resources). Moreover, basin closure status may be seen as a phase beyond a ‘mature water economy’, indicating the onset of an ‘emergency’ phase. In this research paper, we present a case study of a closed basin that has reached the limit where no additional water sources are foreseen, and in which economic instruments (reallocation, volumetric pricing, water rights markets, etc.) and technical strategies (water saving, improved water productivity and water efficiency) have already been widely implemented. 3. Characterisation of the Guadalquivir RB, Closure Process and Main Responses The Guadalquivir RB, which is representative of the Mediterranean region, contains 23% of the total irrigated area in Spain [ 7 ]. The competitiveness of its agriculture, with a focus on high value crops in a context of water scarcity, explains the remarkable expansion in irrigated areas and modernisation of irrigation systems in recent decades, to the point where there are now more than 850,000 hectares of irrigated land. The Guadalquivir is the longest river in southern Spain, with a length of about 650 km and a basin extension of over 57,527 km 2 . Land in the basin is divided between forests (49.1%), agriculture (47.2%), urban areas (1.9%) and wetlands (1.8%). The basin has a Mediterranean climate with an average rainfall of 573 mm, occasional periods of prolonged drought, and an average annual temperature of 16.8 ◦C. Irrigation in Spain has a long and complex history and the analysis of national-scale data reveals no clear patterns of change as the present agricultural systems are very heterogeneous. The north has a continental climate and farmers grow commodity crops (i.e., maize, sugar beet), whereas in the southeast farmers face extremely arid conditions and tend to specialise in out-of-season intensive fruit and vegetable cultivation. Agriculture in the Guadalquivir RB centers on high value crops, which represents a mid-point between the extremely intensive system in the southeast and the low-productivity irrigation in northern basins. The current reservoir capacity in the Guadalquivir RB is 8600 hm 3 and the average water use in the basin amounts to about 3800 hm 3 per year [ 8 ], of which about 3400 hm 3 goes to meet the demand of irrigated agriculture (which represents 85% of the total water demand in the basin). The Guadalquivir Hydrological Plans for both the first period under analysis (2010–2015) and the current one (2015–2021), declare that the level of consumption has reached its maximum and that no significant supply increases are foreseen in the years to come. Against this backdrop, demand management has become the only available tool to manage water demand in the different socio-economic sectors, including agriculture [ 9 ]. Thus, the use of more efficient irrigation techniques plays a key role in achieving water-saving objectives, especially in a context of continuing pressure to increase irrigated areas, despite the explicit administrative moratorium on any further transformation of rain-fed lands into irrigated farmland. The most relevant change in recent decades has been the continuing transformation of rain-fed olive groves to groves irrigated by drip systems. According to the Spanish Ministry of Agriculture [ 7 ], the average value of olive production in the Guadalquivir RB is 1300 EUR/ha for rain-fed olives and Water 2017,9, 136 4 of 15 2500 EUR/ha for irrigated olives. Irrigated olive crops make up 52% of the basin irrigated area (46% in 2005), followed by extensive crops (30%). The latter includes winter cereals (14%), sunflower (6%), cotton (6%) and corn (3%). Other important crops in the basin are fruits, which cover 7% of the total irrigated area, and rice, which represents 4%. As shown in Figure 1, the irrigated area in the Guadalquivir basin has increased continuously over the past two decades, mainly through the abovementioned conversion of rain-fed olive groves into irrigated groves. The rate of conversion from rain-fed to irrigated farmland reached markedly high levels in the second half of the 1990s, when the extreme drought that occurred between 1992 and 1994 drove many rain-fed farms (especially those with olive groves) to convert to irrigation systems by means of private initiatives. In 2005, an administrative moratorium was declared on new irrigated areas in the main subbasin (comprising 90% of the irrigated area), with marginal increases in irrigated areas still allowed in the remaining 10% of the basin. The impact of this moratorium is reflected in in the reduction of the average annual growth rate of irrigated areas, from 9% in the period 1989–2005 to 0.8% in the subsequent period. Water2017,9,1364of14 2005),followedbyextensivecrops(30%).Thelatterincludeswintercereals(14%),sunflower(6%), cotton(6%)andcorn(3%).Otherimportantcropsinthebasinarefruits,whichcover7%ofthetotal irrigatedarea,andrice,whichrepresents4%. AsshowninFigure1,theirrigatedareaintheGuadalquivirbasinhasincreasedcontinuously overthepasttwodecades,mainlythroughtheabovementionedconversionofrain‐fedolivegroves intoirrigatedgroves.Therateofconversionfromrain‐fedtoirrigatedfarmlandreachedmarkedly highlevelsinthesecondhalfofthe1990s,whentheextremedroughtthatoccurredbetween1992 and1994drovemanyrain‐fedfarms(especiallythosewitholivegroves)toconverttoirrigation systemsbymeansofprivateinitiatives.In2005,anadministrativemoratoriumwasdeclaredonnew irrigatedareasinthemainsubbasin(comprising90%oftheirrigatedarea),withmarginalincreases inirrigatedareasstillallowedintheremaining10%ofthebasin.Theimpactofthismoratoriumis reflectedininthereductionoftheaverageannualgrowthrateofirrigatedareas,from9%inthe period1989–2005to0.8%inthesubsequentperiod.  Figure1.Averageirrigationrightsandirrigatedarea.Source:Ownelaborationusingdatafromthe GuadalquivirBasinAuthorityandIrrigationInventories.Adjustedpolynomialtrendlinesareshown inordertodescribethetrajectoryfollowedbyirrigatedarea(solidtrendline)andbyaverage irrigationrights(dottedtrendline). Figure1illustratesthereductionintheaveragewaterrightsforirrigation(m3perha)resulting fromthedepletionofwaterresourcesinthebasin,fallingfromanannualwaterallotmentof9800m3 perhectarein1987to3400m3perhectarein2012[8].Farmershaveadaptedtothisreductioninwater rightsbymodernising,investinginWCTsandusingdeficitirrigation(DI)strategies.The modernisationprocessofirrigationtechniqueshasplayedadecisiveroleinthesignificantincrease inirrigationwaterproductivityinrecentdecades.Thefactthattheirrigatedareainthebasindoubled atthesametimeasadrasticreductiontookplaceintheaverageirrigationrightsperhectarecanonly beexplainedbythemajorinvestmentsmadeinWCTs.Inthiscontext,thegreaterwater‐useefficiency asanexpectedeffectofirrigationmodernisation,alongwithfarmers’increasingcommitmenttocrops withamoreefficientwaterconsumptionandgreatercapacitytogeneratehighagriculturalyields (i.e.,olivegroves),havehelpedthebasintoreachhighefficiencylevelsintheuseofthescarcewater resourcesavailable. ThemodernisationofirrigatedagricultureintheGuadalquivirRBinrecentyearshasbeen promotedbytheregionalgovernmentthroughtheAndalusianIrrigationPlan(1995–2008)andwith resourcesfromtheSpanishnationalgovernment.Thisplanprioritisedthemodernisationofirrigation techniquesinordertobothenhancefarms’competitivenessandtoensurethesustainabilityof farmers’incomes.Throughtheplan,43%oftheexistingirrigationsystemsweremodernisedin1997, andwaterconsumptionbyirrigatedagriculturewasreducedby435hm3peryear,afigurethat exceededforecastsmadewhentheplanwasbeingdeveloped[10,11].TheIrrigationAgendaH‐2015 200 300 400 500 600 700 800 900 1000 1987 1992 1995 1999 2002 2004 2005 2008 2015 2021 2027 Irrigationrights(mm.) Irrigatedarea(th.ha.) 1987‐2015(mm.) 1987‐2015(th.ha) PH2015(th.ha) PH2015(mm.) Figure 1. Average irrigation rights and irrigated area. Source: Own elaboration using data from the Guadalquivir Basin Authority and Irrigation Inventories. Adjusted polynomial trend lines are shown in order to describe the trajectory followed by irrigated area (solid trend line) and by average irrigation rights (dotted trend line). Figure 1illustrates the reduction in the average water rights for irrigation (m 3 per ha) resulting from the depletion of water resources in the basin, falling from an annual water allotment of 9800 m 3 per hectare in 1987 to 3400 m 3 per hectare in 2012 [ 8 ]. Farmers have adapted to this reduction in water rights by modernising, investing in WCTs and using deficit irrigation (DI) strategies. The modernisation process of irrigation techniques has played a decisive role in the significant increase in irrigation water productivity in recent decades. The fact that the irrigated area in the basin doubled at the same time as a drastic reduction took place in the average irrigation rights per hectare can only be explained by the major investments made in WCTs. In this context, the greater water-use efficiency as an expected effect of irrigation modernisation, along with farmers’ increasing commitment to crops with a more efficient water consumption and greater capacity to generate high agricultural yields (i.e., olive groves), have helped the basin to reach high efficiency levels in the use of the scarce water resources available. The modernisation of irrigated agriculture in the Guadalquivir RB in recent years has been promoted by the regional government through the Andalusian Irrigation Plan (1995–2008) and with resources from the Spanish national government. This plan prioritised the modernisation of irrigation techniques in order to both enhance farms’ competitiveness and to ensure the sustainability of Water 2017,9, 136 5 of 15 farmers’ incomes. Through the plan, 43% of the existing irrigation systems were modernised in 1997, and water consumption by irrigated agriculture was reduced by 435 hm3per year, a figure that exceeded forecasts made when the plan was being developed [ 10 , 11 ]. The Irrigation Agenda H-2015 for Andalusia aimed to complete the work begun with the previous plan, by modernising more than 396,000 hectares of irrigated land and achieving expected water savings of about 352 hm 3 per year. The investment for Andalusia (where the Guadalquivir RB accounts for 85% of the total irrigated area) was estimated at 1.54 billion EUR (of which 59% was publicly subsidised) for 347,234 ha (representing an average investment of 4438 EUR/ha) in the analysed period [ 12 ]. According to Corominas and Cuevas [ 12 ], water efficiency (defined as the amount of water productively used divided by the total water supply) in the modernised areas in the Guadalquivir RB has risen from 0.67 to 0.84. Among the more widespread initiatives in this modernisation process, the most important measures are the modification of irrigation networks by the implementation of drip irrigation systems, the construction of small ‘in-farm’ reservoirs to regulate water use, and the implementation of volumetric metering and water consumption control systems. Similarly, many irrigated olive groves have incorporated pumping stations and filtration systems (which are essential to drip irrigation systems), along with automated irrigation systems [13]. The intense modernisation process in the Guadalquivir RB is reflected in the continuous increase in the surface area of drip-irrigated land in the basin (Table 1). It is currently the primary irrigation method in the RB as it is employed in 66% of the total irrigated area, up from 12% in 1989. The comparison at a national level highlights the intense process of modernisation that has taken place in the Guadalquivir RB, which is well ahead of the rest of Spain in this regard. We would argue that the greater degree of mechanisation and modernisation achieved in the Guadalquivir RB is reflective of the high level of agronomic development reached, and is typical of closed RBs. Table 1. Irrigation techniques in the Guadalquivir river basin (RB). 1989 11999 22002 22004 22008 3 Gravity 61% 45% 40% 38% 22% Sprinkler 27% 20% 22% 17% 12% Drip 12% 35% 38% 45% 66% Notes: Source: 1Agricultural census; 2Irrigation registry; 3Hydrological RB plan [8]. The substantial investments made as part of the intense modernisation process in the basin have also resulted in an increase in water costs in both nominal and real terms, due mainly to the higher energy-use intensity of drip and sprinkler irrigation techniques and having to resort to deeper or more distant sources (Table 2). Broken down by type of crops, the highly technical irrigated olive groves, mostly concentrated in the upper basin area, register an average cost of 0.15 EUR/m 3 , while extensive and semi-intensive irrigation crops in the mid-basin and lower basin area enjoy lower costs of 0.03 EUR/m3for surface water and 0.06 EUR/m3for groundwater [11]. Table 2. Average water cost by source (EUR/m3). Year Increase 2008 vs. 1997 1997 2008 Nominal Real Surface 0.04 0.06 47% 10% Ground 0.09 0.14 52% 15% Regenerated - 0.21 - - Notes: Source: Andalusia’s Council of Agriculture and Fisheries [11]. The greater water use efficiency due to the modernisation of irrigation along with the observed water cost increases has led to significant changes in the composition of major crops cultivated in the basin. Besides the public/private response to water scarcity in terms of investing in WCTs and Water 2017,9, 136 6 of 15 modernisation, farmers have tended to respond by dedicating more land to high value-added crops that use irrigation water more efficiently, with olive and citrus crops being notable examples. Though there is limited information on the changes in yield of the different crops in the specific case of the Guadalquivir RB, a report from Castillo et al. [ 14 ] indicates that the increase in physical yields in modernised areas is similar to the regional average. A reason for this might be that pre-modernisation irrigation schemes were already highly productive and water distribution systems were in an acceptable state. The situation in the Guadalquivir RB is different to that in other Spanish basins such as the Ebro RB, where Lecina et al. [ 15 ] found an increase in productivity of about 28% after modernisation. Nevertheless, Castillo et al. [ 14 ] did find an increase in value added per hectare in the modernised areas due to changes in crops after the modernisation. For our case study, Table 3shows the changes that have occurred in the agriculture of the basin in recent years. The area occupied by olive and citrus crops has registered a considerable increase, while other irrigated crops such as cotton, corn and sugar beet report a significantly reduced presence in the basin. In parallel, the average irrigation water application in the basin fell by approximately 600 m 3 /ha between 2005 and 2012, which affected most of the crops but had a particularly notable impact on traditional olive groves, where the use of DI techniques is more widespread [ 16 ]. Table 3also shows the annual relative irrigation supply (ARIS), i.e., the ratio of water applied to water required, for major crops in the basin; the figures reveal an overall reduction in these ratios for most crops. Data were not available for years prior to the study period, but taking into account the fact that pre-drought (1992–1994) average irrigation endowments amounted to 9500 m 3 /ha, we can safely assume that in the early 1990s, endowments covered more than 100% of irrigation needs in the basin. The extent of DI techniques, especially in the case of olive groves (ARIS 0.41 and 0.61 for traditional and intensive olive crops, respectively), explain the high productivity associated with irrigation in the Guadalquivir RB. Furthermore, and as discussed in the next section, these high levels of productivity could not have been achieved without the water-use efficiency gains delivered by the extensive modernisation of irrigation technology observed in the basin. Table 3. Irrigation rights and annual relative irrigation supply (ARIS) ratios for major crops in the Guadalquivir basin (2005–2012). Major Crops Irrigated Area (ha) Water Rights (m3/ha) ARIS Ratio 2005 2012 2005 2012 2005 2012 Traditional olive groves 380,930 393,277 2281 1500 0.62 0.41 Intensive olive groves - 76,323 - 2250 - 0.61 Cotton 77,020 55,302 6048 5600 0.7 0.65 Cereals 58,427 67,208 1500 2300 0.37 0.57 Vegetables 49,886 51,470 6104 5500 1.03 0.93 Corn 46,404 17,668 6624 6250 0.75 0.7 Fruit trees 24,795 23,927 5386 6000 1.39 1.55 Citrus trees 22,578 38,013 5501 5500 1.13 1.13 Sugar beet 20,185 12,230 3730 4500 0.55 0.67 Sunflower 18,032 23,251 1500 3200 0.31 0.66 Rice 36,092 35,180 14,000 13,000 1.06 0.99 Weighted average m3/ha - - 3949 3392 0.7 0.66 Notes: Source: Own elaboration based on data from the Spanish Ministry of Agriculture, Food and Environment [ 7 ] and Confederación Hidrográfica del Guadalquivir [8]. According to the last two Guadalquivir Hydrological Plans (2009 and 2015), there is no possibility of a significant increase in water supply. A few minor reservoirs are under study but they are only projected to increase their present capacity by 4% (if the proposed increases are eventually approved subject to environmental, technical and economic considerations). Most groundwater reservoirs are under policy control and are designated ‘fully exploited’; therefore, according to the hydrological plans that regulate water use, there is no prospect of additional significant resources and the basin is therefore in a ‘closure’ situation. Water 2017,9, 136 7 of 15 Following the discussion of the main public and private responses to the progressive depletion of the water resource in the basin, the next section analyses the short- and long-term economic consequences of these responses on irrigation water productivity. 4. Impacts on Irrigation Water Productivity Improving water efficiency seems to have been the main public and private institutional response to water scarcity in the Guadalquivir RB since the administrative moratorium in 2005. Although the modernisation process started slowly after the severe drought in the period 1992–1995 [ 17 ], the most intensive period of activity began around 2005, when the largest water user associations (WUA) started the process of upgrading their irrigation infrastructure [ 18 ]. As WCTs boost the water productivity ratio by both increasing the numerator (higher value added in the crop plan) and reducing the denominator (lower water use), they help create a dynamic process of productivity improvement (Figure 2). This basin closure process is illustrated in Figure 2. As WCTs increase irrigation water productivity, the expansion of new irrigated areas consequently leads to increasing pressures on the resource and the basin. As Berbel and Mateos [ 19 ] and Playán and Mateos [ 20 ] state, there is no significant increase in water consumption when WCT investments are accompanied by strict control on the part of the water authority through a moratorium on irrigation expansion. Such control helps prevent situations where savings in water abstraction result in additional water depletion due to the water saved being used in new irrigated areas. In our case study, the Guadalquivir Water Authority has only been partially successful in reducing the growth in irrigated areas, given that the annual growth rate of irrigated areas has decreased from 9% to 0.8% after basin closure in 2005 (Table 4). Nevertheless, since the main modernisation process began in 2005, this process cannot be seen as the cause of irrigation expansion in the case of the Guadalquivir basin. In parallel, the extensive modernisation of irrigation systems has enabled widespread use of DI (as shown in Table 3). DI techniques, as well as the higher efficiency levels achieved in the use of irrigation water due to WCTs, have led to a remarkable increase in the economic productivity of irrigated agriculture. This in turn affects the characteristics of water demand by reducing the elasticity of demand with respect to the increasing water prices [ 21 ]. In this scenario dominated by increasing pressures on water demand and a growing scarcity of the resource, the Guadalquivir RB has reached a state of closure, with no additional water resources to be consumed. Water2017,9,1367of14 4.ImpactsonIrrigationWaterProductivity Improvingwaterefficiencyseemstohavebeenthemainpublicandprivateinstitutional responsetowaterscarcityintheGuadalquivirRBsincetheadministrativemoratoriumin2005. Althoughthemodernisationprocessstartedslowlyaftertheseveredroughtintheperiod1992–1995[17], themostintensiveperiodofactivitybeganaround2005,whenthelargestwateruserassociations (WUA)startedtheprocessofupgradingtheirirrigationinfrastructure[18].AsWCTsboostthewater productivityratiobybothincreasingthenumerator(highervalueaddedinthecropplan)and reducingthedenominator(lowerwateruse),theyhelpcreateadynamicprocessofproductivity improvement(Figure2). ThisbasinclosureprocessisillustratedinFigure2.AsWCTsincreaseirrigationwater productivity,theexpansionofnewirrigatedareasconsequentlyleadstoincreasingpressuresonthe resourceandthebasin.AsBerbelandMateos[19]andPlayánandMateos[20]state,thereisno significantincreaseinwaterconsumptionwhenWCTinvestmentsareaccompaniedbystrictcontrol onthepartofthewaterauthoritythroughamoratoriumonirrigationexpansion.Suchcontrolhelps preventsituationswheresavingsinwaterabstractionresultinadditionalwaterdepletionduetothe watersavedbeingusedinnewirrigatedareas.Inourcasestudy,theGuadalquivirWaterAuthority hasonlybeenpartiallysuccessfulinreducingthegrowthinirrigatedareas,giventhattheannual growthrateofirrigatedareashasdecreasedfrom9%to0.8%afterbasinclosurein2005(Table4). Nevertheless,sincethemainmodernisationprocessbeganin2005,thisprocesscannotbeseenasthe causeofirrigationexpansioninthecaseoftheGuadalquivirbasin. Inparallel,theextensivemodernisationofirrigationsystemshasenabledwidespreaduseofDI (asshowninTable3).DItechniques,aswellasthehigherefficiencylevelsachievedintheuseof irrigationwaterduetoWCTs,haveledtoaremarkableincreaseintheeconomicproductivityof irrigatedagriculture.Thisinturnaffectsthecharacteristicsofwaterdemandbyreducingthe elasticityofdemandwithrespecttotheincreasingwaterprices[21].Inthisscenariodominatedby increasingpressuresonwaterdemandandagrowingscarcityoftheresource,theGuadalquivirRB hasreachedastateofclosure,withnoadditionalwaterresourcestobeconsumed.                    Figure2.Modelofabasinclosureprocess.(AdaptedfromBerbeletal.[18]). WithrespecttoDIandnewcrops,ExpósitoandBerbel[16]studyasampleofolivefarmersin theGuadalquivirRBandconcludethatthemodelthatbestexplainstheirbehaviorcentersonthe maximisationofthevalueofthemarginalproductofwater,consideringittobethetruelimiting factorofproduction.Thisiscontrarytotraditionaltheorythatconsiderslandasthelimitingfactor.  Waterscarcity Increasing irrigated area Increasing supply restrictions Demand pressures Watercost increase Higherefficiency ofirrigation plus Deficitirrigation techniques Pressuresonwaterdemand   Increasesineconomic productivityofirrigation water.  Higherinelasticityof irrigatedwaterdemand withrespecttochangesin watercosts. Basinclosure Changesincrop com p osition Figure 2. Model of a basin closure process. (Adapted from Berbel et al. [18]). Water 2017,9, 136 8 of 15 With respect to DI and new crops, Expósito and Berbel [ 16 ] study a sample of olive farmers in the Guadalquivir RB and conclude that the model that best explains their behavior centers on the maximisation of the value of the marginal product of water, considering it to be the true limiting factor of production. This is contrary to traditional theory that considers land as the limiting factor. The rationale of maximising the productivity of a scarce factor (water) can be observed in the Guadalquivir RB, where farmers generally opt for DI techniques and high-tech irrigation for high value crops, in order to maximise the productivity of all production factors: water, land, labor and capital. As a result, irrigation water productivity has increased dramatically in the Guadalquivir RB in recent decades. Table 4shows the yields obtained by rain-fed and irrigated agriculture in terms of the gross value added (GVA) in the Guadalquivir RB. Data for 1989 and 2005 are obtained from the estimates made by Carrasco et al. [ 22 ], and these are supplemented with our own estimates for 2012. GVA measures have been estimated based on data for prices, crop yields, subsidies and direct costs, all of which have been sourced from the Agricultural and Fisheries Statistics of Andalusia, the Prices and Markets Observatory of Andalusia’s Council of Agriculture and Fisheries (CAP), as well as the Survey of Crops and Agricultural Incomes from the Spanish Ministry of Agriculture, Food and Environment (MAGRAMA). Following Carrasco et al. [ 22 ], we assume that the increase in the economic productivity of irrigated agriculture due to improvements in labor and capital factors (e.g., improved seeds, machinery, etc.) is incorporated in the productivity of land and estimated by the increase over rain-fed farming productivity. Therefore, mean irrigation water productivity may be estimated as the difference between the estimated economic productivity (in terms of GVA generated per hectare) of irrigated agriculture and that of rain-fed farming. As argued by Carrasco et al. [ 22 ], it seems clear that this assumption represents an important limitation, as resulting estimates would be valid only if the sole difference between rain-fed and irrigated agriculture were the amount of water used. In practice, however, it is clear that other differentiating factors, such as the use intensity of physical and human capital involved in crop cultivation, play a relevant role in explaining productivity differences. However, bearing in mind the limitations of this simplification, the estimates presented in Table 4 show the analysis of the main variables related to irrigation and the estimated evolution of mean productivity associated exclusively with irrigation water. Table 4. Irrigation water mean productivity in the Guadalquivir RB. GVA: gross value added. Indicator Annual Increase Rate 1989 2005 2012 1989–2005 2006–2012 [1] GVA of irrigation farming (EUR/ha) 1579 2653 2660 4.00% 0.10% [2] GVA of rain-fed farming (EUR/ha) 416 598 659 2.60% 1.40% [3] Increase in productivity due to irrigation 1163 2055 2001 n/a n/a [3] = [2] −[1] (EUR/ha) [4] Average irrigation water application (m3/ha) 9995 4137 3392 –3.40% –2.60% [5] Irrigation water mean productivity 0.116 0.497 0.603 19.30% 3.00% [5] = [3]/[4] (EUR/m3) [6] Irrigated area (ha) 316,646 801,865 845,986 9.00% 0.80% [7] Rain-fed area (ha) 2,412,091 2,128,952 1,950,853 n/a n/a Notes: Source: Data for 1989 and 1995 from Carrasco et al. [ 22 ]. Own elaboration for 2012. Constant prices (base 2005). Results show how the irrigation water mean productivity has increased from 0.11 EUR/m 3 in 1995 to 0.60 EUR/m 3 in 2012, a cumulative increase of 425%. However, significant differences are observed between the two analysed periods, 1995–2005 and 2006–2012. In the period 1995–2005, a remarkable expansion of irrigated area occurs in the Guadalquivir RB, with a 153% increase recorded (mainly in woody crops such as citrus and olive groves, which represent about 60% of the total increase in Water 2017,9, 136 9 of 15 irrigated area in the RB). This expansion of irrigated areas in the basin, along with a 60% reduction in water consumption per hectare as a result of the modernisation of irrigation techniques, explains the significant increase in the irrigation water mean productivity in the period 1995–2005, rising from 0.11 to 0.49 EUR/m3(345% increase). During the period 2006–2012, the average water consumption per hectare decreases by 20%, to approximately 3400 m 3 /ha, while the capacity of irrigated agriculture to generate greater GVA levels than rain-fed agriculture remains largely unchanged (2001 EUR/ha. in 2012 compared to 2055 EUR/ha. in 2005). In our opinion, this would seem to indicate that the observed increase in the irrigation water mean productivity (from 0.49 to 0.60 EUR/m 3 ) in this period can be explained almost exclusively by the higher production efficiency of irrigated farming, which is thus able to generate the same yield levels with lower levels of water consumption. In this regard, the capacity of the Guadalquivir RB to increase GVA through irrigation tends to level out in terms of GVA per irrigation unit. As a result of the marked expansion of irrigation agriculture in the basin, water resources have become the limiting production factor, in contrast with the traditional model that defines land as the limiting factor. Since the degree of modernisation and efficiency of irrigation techniques in the Guadalquivir RB is already high, the ability of irrigated farming to continue generating greater GVA declines, a situation which characterises the current closure of the basin. Figure 3highlights this process by showing the evolution of indexes constructed for the GVA of irrigated farming, consumption of irrigation water and irrigation rights in the period 1989–2012, taking 1989 as the base year (1989 = 100). Water2017,9,1369of14 EUR/ha.in2005).Inouropinion,thiswouldseemtoindicatethattheobservedincreaseinthe irrigationwatermeanproductivity(from0.49to0.60EUR/m3)inthisperiodcanbeexplainedalmost exclusivelybythehigherproductionefficiencyofirrigatedfarming,whichisthusabletogenerate thesameyieldlevelswithlowerlevelsofwaterconsumption. Inthisregard,thecapacityoftheGuadalquivirRBtoincreaseGVAthroughirrigationtendsto leveloutintermsofGVAperirrigationunit.Asaresultofthemarkedexpansionofirrigation agricultureinthebasin,waterresourceshavebecomethelimitingproductionfactor,incontrastwith thetraditionalmodelthatdefineslandasthelimitingfactor.Sincethedegreeofmodernisationand efficiencyofirrigationtechniquesintheGuadalquivirRBisalreadyhigh,theabilityofirrigated farmingtocontinuegeneratinggreaterGVAdeclines,asituationwhichcharacterisesthecurrent closureofthebasin.Figure3highlightsthisprocessbyshowingtheevolutionofindexesconstructed fortheGVAofirrigatedfarming,consumptionofirrigationwaterandirrigationrightsintheperiod 1989–2012,taking1989asthebaseyear(1989=100).  Figure3.Indexesofwaterconsumption,irrigationrightsandGVA.Note:Baseyear1989=100. ThewatermeanproductivityofmajorcropsintheGuadalquivirRBisquiteheterogeneous. Table5showsthe2012dataonGVAperhectareformajorirrigatedandrain‐fedcrops,obtainedby applyingasimilarmethodtothatusedpreviouslytoestimateirrigationwaterproductivityinthe basin(Table4).EstimatesshowthatthehighestGVA‐to‐irrigationwaterratioisachievedbyolive andcitruscrops.Thesecropshaveregisteredthelargestincreaseincultivatedareaovertheanalysed period,accountingnowadaysformorethan60%oftotalirrigatedareaintheGuadalquivirRB. AccordingtoCastilloetal.[14],pricesofmajorcropsintheGuadalquivirRBhavedecreasedinreal termsinthelasttwodecades,andthisreductioninpricehasnotbeenfullyoffsetbytheincreasein physicalproduction,meaningthatincomeperhectarehasdecreasedinrealterms.Farmershave reactedtothissituationbyswitchingfromcommoditycrops(i.e.cereals,sugarbeet,cotton)tohigher valuecrops(i.e.,citrus,olive). Thus,theincreaseintheareadedicatedtothecultivationofhigh‐productivyirrigatedcrops observedinrecentyearscouldbeexplainedbytheirhigherGVA‐to‐irrigationwaterratiocompared toalternativecrops.Thisincreaseaddstothepressureonthescarcewaterresourcesandreinforces thebasinclosurecycle. Theanalysisofourcasestudyhasclearlyrevealedhowgreaterresource‐useefficiencyhasled totheexpansionofirrigatedareasofthosecropswithhigherlevelsofGVAperirrigationunit(i.e., oliveandcitruscrops).Inouropinion,thedecliningcapacityofirrigatedfarminginthebasinto generategreaterGVAperhectare,asshownbytheslowingrateofaverageannualincreasein irrigationwatermeanproductivityintheperiod2005–2012,wouldexplainthepresentsituationin theGuadalquivirRB.Thisslow‐downinproductivitygainsreflectsthediminishingreturnstoscale oftechnicalinnovation,withDI,cropchangeandirrigationmodernisationreachingthelimitsoftheir 0 50 100 150 200 250 300 350 400 450 500 1989 1992 1995 1998 2001 2004 2007 2010 2013 Consumption GVA Irrigationrights Figure 3. Indexes of water consumption, irrigation rights and GVA. Note: Base year 1989 = 100. The water mean productivity of major crops in the Guadalquivir RB is quite heterogeneous. Table 5shows the 2012 data on GVA per hectare for major irrigated and rain-fed crops, obtained by applying a similar method to that used previously to estimate irrigation water productivity in the basin (Table 4). Estimates show that the highest GVA-to-irrigation water ratio is achieved by olive and citrus crops. These crops have registered the largest increase in cultivated area over the analysed period, accounting nowadays for more than 60% of total irrigated area in the Guadalquivir RB. According to Castillo et al. [ 14 ], prices of major crops in the Guadalquivir RB have decreased in real terms in the last two decades, and this reduction in price has not been fully offset by the increase in physical production, meaning that income per hectare has decreased in real terms. Farmers have reacted to this situation by switching from commodity crops (i.e., cereals, sugar beet, cotton) to higher value crops (i.e., citrus, olive). Thus, the increase in the area dedicated to the cultivation of high-productivy irrigated crops observed in recent years could be explained by their higher GVA-to-irrigation water ratio compared to