Development of a decision support system for the estimation of surface water pollution risk from olive mill waste discharges

According to the Water Framework Directive (WFD, 2000/60/EC), Integrated River Basin Management Plans (RBMP) are required at different scales, in order to prevent amongst other things, water resource deterioration and ensure water pollution reduction. An integrated river basin management approach underpins a risk-based land management framework for all activities within a spatial land-use planning framework. To this end, a risk assessment methodology is required to identify water pollution hazards in order to set appropriate environmental objectives and in turn design suitable mitigation measures. Surface water pollution as a result of Olive Mill Waste (OMW) discharge is a serious hazard in the olive oil producing regions of the Mediterranean. However, there is no standardised method to assess the risk of water pollution from olive mill waste for any given river basin. The present chapter shows the results from a study conducted addressing the above issue by designing a detailed risk assessment methodology, which utilises GIS modelling to classify within a watershed individual sub-catchment risk of water pollution occurring from olive mill waste discharges. The chapter presents the proposed criteria and calculations required to estimate sub-catchment risk significance and comments on the methods potential for wider application. It combines elements from risk assessment frameworks, Multi Criteria Analysis (MCA), and Geographic Information Systems (GIS). MCA is used to aggregate different aspects and elements associated with this environmental problem, while GIS modeling tools helped in obtaining many criterion values and providing insight into how different objects interact in nature and how these interactions influence risk at the watershed level. The proposed method was trialed in the Keritis watershed in Crete, Greece and the results indicated that this method has the potential to be a useful guide to prioritise risk management actions and mitigation measures which can subsequently be incorporated in river basin management plans.