Prospects for Improving Gravity-Fed Surface Irrigation Systems in Mediterranean European Contexts

Abstract

Traditionally, most irrigation practices in Southern Europe have been based on gravity-fed surface irrigation systems. Currently, these systems remain a relevant typology in the European Union (EU) member states of the Mediterranean areas, where it is often the only sustainable method for farmers due to the small size of agricultural holdings, their reduced capacity and readiness to invest and the low ratio between yield profits and irrigation costs. In the last several years, in response to European and national directives, surface irrigation has garnered increasing attention at the political and bureaucratic levels due to frequent criticisms of its postulated low efficiency and high water wastage. However, these systems commonly provide a number of ecosystem services and nature-based solutions that increase the positive externalities in different rural socio-ecological contexts and often have the potential to extend these services and provide solutions that are compatible with economical sustainability. This study aims to discuss the prospects for new practices and for the rehabilitation and modernization of the gravity-fed surface irrigation systems in EU Mediterranean areas to enhance water efficiency, thus gaining both economic advantages and environmental benefits. The difficulties, stimuli for improvements and peculiarities of the irrigation water management of four rural environments located in Italy, Spain and Portugal were analyzed and compared to the current state of the gravity-fed surface irrigation systems with hypothetical future improvements achievable by innovative technologies and practices. In these different case studies, the current gravity-fed surface irrigation systems have an obsolete regulatory structure; water-use efficiency is not a driving criterion for the management of the conveyance and distribution canal network, and farmers are not yet adequately encouraged to adopt more efficient gravity-fed irrigation practices. A continuous knowledge exchange is thus necessary for the interaction of all irrigation water managers and farmers to improve their eco-efficiency and to preserve and promote their cultural heritage across the entire water supply and delivery chains. We argue that the best way forward will require precisely targeted rehabilitation measures of gravity-fed surface irrigation systems based on the integrated use of decision support services, gate automation, remote and feedback controls and real-time flow optimization.

Evaluating Gravity-Flow Irrigation with Lessons from Yuma, Arizona, USA

“…These changes have led to actual, overall water conservation. Yuma is a unique agronomic area, so it may be difficult to replicate its success in other areas [7]. Yet, the case study of Yuma illustrates that growers can and do make a host of innovative adaptations in gravity-based systems when there are economic incentives to do so.…”

“…The ecosystem services of such return flows can be important for maintaining riparian species. Many riparian systems now depend on these return flows, which are subject to changes in managed, hydrological systems that have been altered to accommodate human water uses [7,[62][63][64][65][66][67]. Thus, what may seem a rational response to water scarcity by irrigators at the farm level may exacerbate water scarcity problems at the basin scale.…”

“…Despite this characterization, gravity flow remains the most prevalent mode of irrigation worldwide, largely because of the low energy requirements relative to alternatives [7]. It remains the dominant mode of irrigation, even among developed countries in regions such as southern Europe and the western United States [7,8].…”

“…It is true that pressurized irrigation systems (such as sprinkler or drip) can achieve higher levels of on-farm application efficiency than traditional gravity systems. Yet, there are also counter-examples throughout the world of farming systems that have achieved high levels of on-farm application efficiency [7,[9][10][11]. The management of gravity systems is not static.…”

“…The management of gravity systems is not static. Farmers support and experiment with quite sophisticated systems, such as ones relying on computerization, automation, and real-time optimization [7,[9][10][11][12][13][14][15][16]. Further, simple measures of on-farm application efficiency ignore more comprehensive aspects of basin-wide efficiency ditch has "gates" or "valves" installed in the side of the ditch, which are opened to release water from the ditch into furrows or into a border.…”