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Freiburger Geographische Hefte, Heft 68

Philipp Weckenbrock (2011): Making a virtue of necessity - wastewater irrigation in a periurban area near Faisalabad, Pakistan A GIS based analysis of long-term effects on agriculture.

In view of rapidly growing populations especially in so-called developing countries, the pressure on the existing freshwater resources is bound to increase. In particular agriculture, the sector with the highest demand for freshwater, is facing growing water scarcity. At the same time, rapid urbanisation processes result in increasing volumes of wastewater, most of which are not treated adequately. In periurban areas of many cities of the South, farmers are making a virtue of necessity by using untreated wastewater to irrigate their fields. Many scientists, politicians and planners still associate mainly health and environmental risks with this type of irrigation. However, the positive aspects and potential of wastewater use in agriculture are increasingly being recognised. This is related to a broadening of research on the topic from an exclusive focus on health risks to a wider perspective which includes benefits of wastewater irrigation. So far, only a limited amount of information about long-term impacts of wastewater irrigation on agriculture exists. For this case study from a periurban area of the Pakistani city of Faisalabad, a set of different methods was used. These include group discussions, semi-structured interviews and field mapping as well as an analysis of land use records retrieved from the local revenue authority. These records cover a period of 50 years beginning in the 1950s and are characterised by high spatial and temporal resolutions. Methods to process the records for analyses are developed. In particular the transformation of this analogue GIS into a digital GIS offers various possibilities for long-term analyses which have not previously been used for published scientific studies. The focus of the study is on impacts of long-term wastewater irrigation on ecological and economic aspects of agricultural sustainability. For this purpose, the predominantly wastewater irrigated agriculture of the village Chakera is compared with the predominantly groundwater irrigated agriculture of the neighbouring village Kehala. Since Chakera farmers had access to an unlimited supply of untreated wastewater, they could use the hot, dry summer season as a fully-fledged second cropping season. In this way, they could double the proportion of areas under cultivation to barren areas within two years after the turn of the millennium. Since then, the agricultural intensity in Chakera was higher than in Kehala for the first time since the 1960s. Also with regard to economic aspects of agriculture, wastewater gave Chakera farmers an advantage over their Kehala neighbours who paid up to 20 times more for groundwater than Chakera farmers for wastewater. Moreover, wastewater irrigated areas were characterised by higher economic outputs than non-wastewater irrigated areas. This was due to the increased intensity of cultivation and a trend towards higher value crops such as vegetables. In contrast to assumptions voiced in several scientific publications, the crop diversity of wastewater irrigated fields was generally higher than that of non-wastewater irrigated fields. Thus this study – contrary to expectations – finds positive impacts of long-term wastewater irrigation on indicators of economic and ecological agricultural sustainability in the research area. This is in line with the predominantly positive assessment of wastewater irrigation by Chakera farmers which is based on practical experience from several decades.

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