Quantitative sustainability and qualitative concerns in an irrigations system using recycled water to supplement limited groundwater supply

Conference Paper

2013

Published in: Soil and irrigation sustainability practices

Alataway, John Gowing and Abed . 2013

Sustainability of irrigation in a country facing water scarcity depends upon adoption of best management practices
to deliver ’more crop per drop’ together with use of recycled waste-water from urban sewage systems. Saudi
Arabia is a country facing extreme water scarcity and in this paper we report on research conducted at an extensive
irrigation system where a concerted effort over several years has been devoted to achieving a high level of water
productivity. Al-Ahsa oasis is located about 60 km inland from the Persian Gulf and has been inhabited since
prehistoric times, due to the abundance of water in an otherwise arid region. It is one of the largest oases in the
world with 12,000 hectares of irrigated land and more than 2 million palm trees. Historically the oasis was watered
by over 60 artesian springs, but water is now pumped from the aquifer. To supplement this groundwater source,
treated waste-water reuse has been practiced since 1992 and now comprises 30% of total supply. In addition, a
comparable amount of agricultural drainage water is collected and recycled, so that the ’first-use’ water represents
only 40% of total irrigation supply. While this re-use system permits sustained irrigation with greatly reduced
groundwater abstraction, there is a potential down-side in that fertilizers and contaminants applied with irrigation
water move through the soil and return to the irrigation supply enhancing the risk for human and animal health. We
investigated this problem using E coli and helminth eggs as indicators of human health risk. We sampled each of the
three sources which are delivered separately to the head of the main irrigation canal where they are blended. The
groundwater was free from E coli and helminths and the treated wastewater source was generally within designated
quality standards. The recycled drainage water was delivered untreated into the canal system and was found to be
contaminated with both E coli and helminths above acceptable standards. Sampling from the canal system showed
that there was a general increase of E coli concentration with distance downstream representing an increasing risk
to human health from consumption of sensitive crops. Reasons for this trend were explored with the most likely
explanation being the use of contaminated drainage water. Natural processes of soil filtration were not providing
adequate decontamination of drainage water.

• Publication Work Type: ورقة علمية
• Conference Location: Soil and irrigation sustainability practice
• Conference Name: European Geosciences Union General Assembly
• Sponsoring Organization: Vienna: Austria