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Box 4-3:  Ecological impacts of over-abstraction on wetland and riverine ecosystems in Spain

Sources: (Arroita et al., 2015; Benejam et al., 2010; De Stefano et al., 2015; EC, 2019c; Green et al., 2016; Muñoz-Reinoso, 2001; OECD, 2019, 2015; WWF, 2006, 2016; UNESCO, 2020)

Unauthorised water abstraction from groundwater is considered a significant problem in Spain. It is estimated that wells and boreholes without a permit by the competent river basin authority exceed 500 000 and, potentially, they account for 40 to 50 % of total groundwater abstractions. Furthermore, Spanish authorities have detected cases of licensed users, who are abstracting more than their allocated quota. Unauthorised water abstraction in Spain has been mainly driven by uncontrolled expansion of irrigated agriculture, urban developments and tourism facilities (e.g. golf courses). The problem has existed for decades, leaving a legacy of over-exploited aquifers across the country. The problem is also related to the existence of “senior water rights” (i.e. old water rights granted decades ago), which have not been revised to account for updated studies on water balances and water needs. Over-abstraction has impacted various riverine and wetland ecosystems.

The Doñana National Park is an important coastal wetland, designated as UNESCO World Heritage site, which lies at the delta of the Guadalquivir River and covers 54,252 ha of lagoons, salt marshes, fixed and mobile dunes, scrub woodland and maquis. Over the past decades, there have been land conversions for irrigated agriculture and touristic facilities in the periphery of the park.The expansion of irrigation has been particularly driven by the expansion of rice and strawberry fields. Both cultivations require a high amount of irrigation, and their production is largely exported to foreign countries. Over-abstraction for irrigation has resulted in the decline of the groundwater tables in several parts of the region, the depletion of temporary ponds, the decrease of local stream flows the reduction of groundwater recharge. In coastal areas, the groundwater-sea water equilibrium has been distorted, resulting in saline intrusion. The Doñana area is also suffering from nutrients and chemicals released from agricultural activities and heavy metals originating from upstream industrial activities. The over-exploitation of aquifers and the decrease of stream flows limits their capacity to dilute and flush out pollutants; thus, pollution problems like eutrophication are favoured. Overall, the natural ecosystem faces negative impacts, which may be observed in the alteration of vegetation (e.g. increase of xeric shrubs, pine trees and juniper woodland), the distortion of invertebrate communities (e.g. dragon flies), the decline of fish, molluscs and birds species (e.g. wintering and nesting ducks, and coots), and the spread of invasive over native species. The river basin authorities have launched several proceedings for identified breaches and closed a limited number of illegal wells in the past. However, in 2019, the European Commission decided to refer Spain to the European Court of Justice for insufficient action and alleged breaches of the WFD and the Birds and Habitats Directives.

Research studies on Spanish rivers have also shown that the natural flow regime has been significantly altered in various river basins. Over-abstraction has turned normally perennial rivers into intermittent flowing streams., and fish assemblages were seriously impacted on sites with high pressure from water abstraction. Reduction in carbon storage and breakdown, as well as in the population of shredder insects, were also observed in mountain streams affected by over-abstraction.

The friction between environmental and economic water demands is illustrated by the case of the River Basin Management Plan of the Tagus River in Spain. The current plan, in force from 2015 to 2021, did not effectively take environmental water demand into account, favoring economic functions (especially irrigated agriculture). In 2016, a group of civil associations and representatives of local municipalities submitted a legal challenge to the plan. In its 2019 ruling, the Spanish Supreme Court annulled the plan's provisions on environmental flows and required the River Basin Authority to enact urgent interim measures to cover the period until the start of the next planning cycle in December 2021.