WATER PRODUCTIVITY, HEALTH AND SUSTAINABLE AGRICULTURE: IMPROVING THE PERFORMANCE OF WASTEWATER IRRIGATION IN PERI-URBAN AREAS OF PAKISTAN

Theme 3: Agriculture, Water and Cities

Water and nutrient balance: The results of the study clearly showed that wastewater is a more reliable and flexible source of irrigation water than regular canal water. Farmers who used wastewater irrigated more often and were able to apply more water per irrigation application as compared to non-wastewater farmers. Through the application of wastewater, chemical fertilizer input was reduced to less than 65 kg/hectare. In total the farmers at the Narwala Road site saved Rs 3,000,000 (US$55,000) or seven times the wastewater fee that they had to pay to the local Water and Sanitation Agency It was estimated that a farmer using untreated wastewater in Pakistan earns Rs 35,000 (US$600) more than a non-wastewater farmer.

Health survey - Vector-breeding: The presence of potential vectors of human diseases indicated that wastewater systems could contribute to vector-borne disease risks in addition to other associated health risks for poor human communities that depend on wastewater use for their livelihoods. The vegetation and floating waste of poorly managed systems offers ideal habitats for the breeding of mosquitoes by attracting them for oviposition and also by providing protection against predators. The creation of such perennial water bodies close to large urban areas in an arid environment could pose a significant health risk for communities living around such treatment schemes.

Health survey - Intestinal nematode and protozoa infections: The study showed no increased risk for children of wastewater farmers as compared to children of textile laborers and farmers using regular irrigation water, which is contradictory to similar studies in Mexico and Morocco. The study also showed no increased risk of roundworm infections in wastewater farmers but there was an almost six-fold increase in risk of hookworm infections in wastewater farmers as compared to the two unexposed groups.

Heavy metal accumulation and plant up-take: The results indicate that for both the CH4 and Dhudi Wala Minor irrigated fields, soil, Cd, Pb, Zn, Ni, Cr and Cu concentrations are all below EEC MP levels, irrespective of sampling location. However, elevated levels of Zn and Cd were observed at two sampling locations. Wheat grain Cd concentrations exceeded the Joint FAO/WHO Expert Committee on Food Additives (JECFA) MP level of Cd in wheat grain of 0.1 mg kg-1. However, Chaney et al. (1996) suggested that a Cd:Zn ratio of <1.5 effectively provides protection against Cd-induced health impacts. For the CH4 and Dhudi Wala Minor wheat samples, the Cd:Zn ratio ranged from 0.28–1.05%. Health risks are therefore effectively prevented at this time.

Nationwide survey: The results showed that untreated wastewater was used for irrigation in approximately 80 percent of all urban centers with a population > 10,000 inhabitants. The total area in which untreated wastewater was used for irrigation was over 32,000 hectares and approximately 20,000 farming families relied on untreated wastewater use for their livelihoods. Vegetables were the most commonly grown crop and were cultivated all year round in all cities. Other major wastewater crops were fodder (sorghum bicolor), wheat, cotton, sugarcane and rice.