Multi-Criteria Decision Analysis of Treated Wastewater Use for Agriculture in Water Deficit Regions1

Al-Juaidi, Ahmed E., Jagath J. Kaluarachchi, and Ungtae Kim, 2010. Multi-Criteria Decision Analysis of Treated Wastewater Use for Agriculture in Water Deficit Regions. Journal of the American Water Resources Association (JAWRA) 46(2):395-411. DOI: 10.1111/j.1752-1688.2009.00409.x Abstract: Coastal regions such as the Gaza Strip of Palestine with limited freshwater supply suffer significantly due to the rapid depletion of water levels, seawater intrusion, and increased water demands. In such regions, use of treated wastewater (TWW) is a viable option if public health issues are addressed. The goal of this paper is to address the use of TWW in agriculture while considering net benefit, economic efficiency of water use (EEWU), environmental goals, and public health risks. The proposed methodology considers public health risk assessment and multi-criteria decision analysis to assess the beneficial use of TWW in agriculture. The methodology was demonstrated for the Gaza Strip. The health risk assessment suggests that increasing the elapsed time between irrigation and consumption and switching from surface to sprinkler and drip irrigation are practical measures to reduce public health risks. The optimization and decision analyses show that proper allocation of freshwater and TWW and distribution of land area by crop type can significantly increase the net benefit and EEWU. In most cases, net benefit increased by 44%, groundwater use reduced 29% while increasing the EEWU by threefold compared with the existing conditions. The multi-criteria decision analysis with weighted goal programming can develop flexible management options that considers a given decision-maker preference. When groundwater abstraction for agriculture reduced from 57 to 36 Mm³ as per decision analysis, the corresponding area below mean sea level decreased by 58% indicating significant aquifer recovery.     

Tradeoffs between soil, water, and carbon -- a national scale analysis from New Zealand

The tradeoffs between the regulation of soil erosion, provision of fresh water, and climate regulation associated with new Pinus radiata forests in New Zealand are explored using national models. These three ecosystem services for which there is strong demand are monetised as commodities (avoided soil erosion is NZ $1 per tonne; water is NZ $1 per cubic metre; and sequestered carbon is assumed to be NZ?$73 per tonne). This permits their summation on a spatial basis to produce a national map of the net benefit of these ecosystem services. Net benefit is spatially variable depending primarily on the relative mix of forest growth rates and demand for irrigation water. New P.?radiata forests (once mature) generally reduce mass-movement erosion by an order of magnitude. This provides significant benefits for erosion control where there are high natural rates of erosion. Benefits are especially large in catchments where high sedimentation is increasing flood risk and degrading aquatic ecosystems. The generally high growth rates of P.?radiata in New Zealand (8.5 tonnesCha(-1)yr(-1) on average for existing forest) add significant environmental benefits of carbon sinks to climate regulation. However, the reduction of water yield associated with new forests (between 30% and 50%) can neutralise these benefits in catchments where there is demand for irrigation water, such as the eastern foothills of the Southern Alps and the tussock grasslands in the South Island.     

Applicability of risk-based management and the need for risk-based economic decision analysis at hazardous waste contaminated sites

Decision analysis in subsurface contamination management is generally carried out through a traditional engineering economic viewpoint. However, new advances in human health risk assessment, namely, the probabilistic risk assessment, and the growing awareness of the importance of soft data in the decision-making process, require decision analysis methodologies that are capable of accommodating non-technical and politically biased qualitative information. In this work, we discuss the major limitations of the currently practiced decision analysis framework, which evolves around the definition of risk and cost of risk, and its poor ability to communicate risk-related information. A demonstration using a numerical example was conducted to provide insight on these limitations of the current decision analysis framework. The results from this simple ground water contamination and remediation scenario were identical to those obtained from studies carried out on existing Superfund sites, which suggests serious flaws in the current risk management framework. In order to provide a perspective on how these limitations may be avoided in future formulation of the management framework, more matured and well-accepted approaches to decision analysis in dam safety and the utility industry, where public health and public investment are of great concern, are presented and their applicability in subsurface remediation management is discussed. Finally, in light of the success of the application of risk-based decision analysis in dam safety and the utility industry, potential options for decision analysis in subsurface contamination management are discussed.