Pressurised irrigation cuts consumption in Andalucía
The mild wet winters and extremely dry summers of Andalucía in southern Spain, combined with irrigation, allow farmers to grow summer crops that would otherwise be impossible. Juan Rodriguez-Diaz and Keith Weatherhead, from IFAPA in Spain and Cranfield University in the UK, describe the importance and use of benchmarking for maximising the benefit of limited water supplies for irrigation.Andalucía currently possesses an irrigated surface area of 900,000ha, widely spread through the region (see figure 1). This is 19% of its cropped area and almost 30% of Spain's total irrigated area of 3.3 million ha.
This 19% produces 53% of the final value of agricultural production and 55% of the jobs in the agricultural sector in Andalucía. Hence, water for irrigation is a key factor in Andalucía's economy.
The irrigated cropping is quite heterogeneous. However, a clear differentiation can be made between the littoral (coastal zone), which specializes in horticultural crops of high economic value, because of its milder climate, and the interior, where extensive field crops such as olive trees, cereals, beans, citruses, cotton and sunflower prevail.
High productivity is one reason behind the continuing growth in irrigation area, at about 2% per annum. However, this has led to a significant water deficit, currently around 650 million m3/y. Clearly, better use of irrigation water is needed.
Water policy has traditionally been aimed at increasing supply by investments in infrastructure. In recent years, policy has been largely re-oriented to improving water use with better equipment and converting the old open channels distribution networks into on-demand pressurised networks. One result is that trickle has now become the most important irrigation method in the region.
Benchmarking can help water management by means of comparisons, identifying best practice. Benchmarking and performance indicators for irrigation have been studied at the University of Cordoba in Andalucía since 2001.
Performance indicators are the main tools in the benchmarking process. These are the ratios between basic variables such as water applied, irrigated area, water costs and outputs. By comparing performance indicators, farmers and water managers can determine whether one irrigation district is more or less efficient than another and take the necessary measures to correct any deficiencies.
The performance indicator set developed by the International Programme for Technology and Research in Irrigation and Drainage (IPTRID) was used. This set is composed of 32 indicators divided into four groups: system operation, financial indicators, productive efficiency and environmental performance.
Initially, nine irrigation districts were compared. Eight (Bembézar MD, Bembézar MI, Fuente Palmera, El Villar, Genil-Cabra, Sector B XII and El Rumblar) are located in the interior while Piedras-Guadiana is in the littoral zone and produces crops of high economic value, particularly strawberries and citrus.
The analysis shows that the districts in which users pay for water per unit of irrigated area are usually the largest consumers of water per hectare . In contrast, in districts with a pressurised irrigation network, where revenues are partly collected per cubic metre used, and water is more costly, consumption is significantly lower.
The irrigation districts with pressurised water supplies have the highest management, operation and maintenance (MOM) costs per unit of water supplied, due both to higher energy and higher amortisation costs.
However, the indicator relating the total value of agriculture production to the amount of irrigation water consumed shows that Piedras-Guadiana, on the littoral, is easily the most productive district in terms of water use. In the interior, the districts with pressurised water systems are also more productive per unit of water.
However, when productivity is related to irrigated area, there is less difference, and the districts with older infrastructures sometimes have better productivity per area.
Irrigation in Andalucía is a key wealth generator for the economy. However, water scarcity means that policies aimed at managing demand are a necessity. Use of benchmarking techniques can help lead to a more efficient use of the irrigation water
On-demand pressurised networks, where users must partly pay per unit of irrigation water, have been shown to be effective in saving water. In part, this is due to the fact that users of pressure irrigation systems dedicate a larger percentage of the value of their agricultural production to the cost of water.