Guadalquivir Marshes (Spain)
The case study is the rice-growing area in the Lower Guadalquivir Valley. The area comprises about 35,000 ha of marshes located next to the estuary of the Guadalquivir River and between the river and Doñana National Park (UNESCO Biosphere Reserve). Rice production is traditional in the region; it generates significant rural employment and direct and indirect economic activity (rice industry, machinery, agrochemicals, transport). Land productivity is very high thanks to the environment and high cropping intensity. Average yield is near 10 tons per hectare. Irrigation is by flooding, requiring 10,000 m3/ha/year at district scale, although individual fields may receive three times as much. This requirement means 360 hm3 in 2018, which represents almost 10% of the Guadalquivir basin water abstraction devoted to irrigation. Therefore, rice agro-ecosystems in the Lower Guadalquivir valley are on the focus of all water users and environmentalists in the Guadalquivir basin. The irrigation water comes from the general regulation system of the basin, meaning that there is no specific reservoir serving the rice districts. On the left riverbank, part of the water supply comes from a canal diverting from the Guadalquivir River about 150 km upstream. On the right riverbank, water released for irrigation is pumped directly from the estuary. Salinity is therefore a potential problem which severity depends on the rate of water release. The water used in the rice districts circulates from paddy field to paddy field; it is evapotranspirated; part percolates, feeding the aquifer that underlies the marshes; and the excess returns to the river with concentration of salts that has increased along the water circuit. This particular hydrological setting makes water use in the rice agroecosystems of the Guadalquivir valley critical for the integrated water management of the basin and for meeting the water sustainability and productivity goals. Due to its location near the Atlantic Ocean, district inefficiency cannot be compensated by downstream reuse.
Water restrictions due to rainfall and reservoir storage variability is the main threat for rice production in the Guadalquivir marshes. Recurrent years of water scarcity limit the cropped area and consequently the associated agricultural and agro-industrial socioeconomic activity. In these circumstances, water scarcity is aggravated by salinity. The salinity problem is not uniform across the area but it is spatially distributed, increasing downstream along the estuary. Finally, although integrated pest management is practiced all over the rice growing area, the cropping intensity implies high use of inputs and the consequent emission of greenhouse gases, leaching of agrochemicals and estuary water pollution.
Rice growers and industry are very aware of the pressure to reduce the amount of water they use and to preserve the quality of the return flows. Some years ago, they opted for sustainable intensification and integrated pest management; more recently, water saving is a major concern. District managers on the right riverbank have re-engineered water circulation and delivery, enhancing water re-use and introducing water quality in the control of drainage reuse. The rice industry is currently investing in R&D by testing water saving practices in large farms. Irrigation equipment companies are breaking through traditional flood irrigation by promoting aerobic subsurface drip irrigation. These initiatives conform the new open innovation environment where MEDWATERICE has disembarked with novel water saving ideas and an approach of participatory action research.