Wastewater is no longer perceived as purely negative. Instead it has been recognized as a non-conventional source of water offering opportunities to meet the increasing water demand. Our analysis focuses on South Africa, which is a water-scarce country. The agricultural sector here, highly-dependent on rainfall, is affected by changes in the rainfall pattern due to climate change. Water availability is recognized as the single most important limiting factor for agricultural production in the country. The situation is expected to aggravate due to the increasing demand from other sectors (Goldblatt, 2012). In such context, it's central to look for alternative sources and wastewater can serve this purpose. Using a choice experiment (CE) approach this study gets insight into farmers' preferences for the use of wastewater in agricultural irrigation. Our case study region is located nearby Cape Town in Western Cape Province. This region is known for its vineyards, but olives, wheat and fruit trees are also produced. A group of farmers currently already use treated effluent from a municipal treatment plant to irrigate crops. The main drivers for this initiative are the lack of alternative water sources for irrigation and climate change awareness. This case is a successful story of wastewater use in agricultural irrigation in the context of a developing country, from which we can learn important lessons.
We used a choice modelling approach. The first step is the design of the CE following the steps according to Hanley et al. (2001). Second step is the data collection process. We conducted a survey on the field with farmers. Third step is the data analysis and estimation of the model. For this we applied a Latent Class Model (LCM). This model allows accounting for heterogeneity and estimate willingness to pay (WTP). In CEs goods are described based on their 'attributes'. Respondents are asked to choose among alternatives of the goods. In our case the good to be valued is the wastewater reuse structure, with following attributes: 'water quantity-quality', 'practice restrictions', 'scheme model' and 'price'. The fieldwork was conducted between April-July 2014. Respondents were randomly selected. The CE was part of a survey, which contained additional questions on socio-economic characteristics, cropping pattern, irrigation practices and perceptions on wastewater use. A total of 46 respondents participated in the survey.
Results and discussion
For about 80% of the respondents farming is the main occupation. About 37% of the respondents are currently using treated effluent for irrigation. The main crop is wine grapes, in lesser extent olives, fruit trees and wheat. More than half of the respondents say they're interested in using treated effluent for irrigation. On average farmers disagree that irrigation with treated effluent can be a threat for farmers, consumers or the environment. Moreover, on average farmers agree that irrigation with treated effluent should be encouraged by authorities and that's a good alternative source to fight water scarcity. The LCM divided the sample in segment 1 (54.4%) and segment 2 (45.6%). The 'current use of treated effluent' is what differentiates the two segments most: 80% of farmers in segment 2 currently already use treated effluent versus 3.85% in segment 1. In segment 1, the coefficient for level A1 in terms of water quantity-quality is significant and positive. This means that farmers prefer 'strict quality standards' despite the 'limited water quantity' as offered in this alternative compared to the reference level: A4 (Table 1). This isn't the case in segment 2. 'High practice restriction' is significant and negative for both segments compared to the reference of 'low' restrictions (no restriction on crops; no restriction of irrigation methods; regular monitoring). In segment 2, farmers prefer a private-managed scheme over a public scheme. Price is significant and negative for both segments. For WTP estimates, 'high practice restrictions' (both segments) and private scheme model (segment 2) are statistically significant.
We explored farmers' preferences for the framework to use treated effluent through a quantitative approach. Our findings suggest that farmers prefer a privately-managed scheme over a public scheme. This option seems to offer them more trust regarding the management and quality monitoring. Farmers are willing to pay for it. Farmers also prefer strict water quality standards despite that this option implies a reduced water quantity. This suggests that farmers are keen to irrigate crops with treated effluent if 'good-quality water' is guaranteed. Overall, irrigation with treated effluent is well perceived in this area. However, guaranteeing water quality is a main concern in order to avoid problems, which could impact negatively on crop commercialization. This case study offers interesting results to draw lessons for policy formulation on the use of treated effluent in agricultural irrigation.
Table 1 Results of LCM
2. Hanley N., Mourato S., Wright R. (2001) Choice Modelling Approaches: a Superior Alternative for Environmental Valuation? Journal of Economic Surveys, 15(3):435Â–462