A New Approach to Selecting Optimum Locations of Sampling Stations in Karkheh Dam Reservoir Using CE-QUAL-W2 Model

Preservation and optimal usage of water resources are that main aspects of sustainable development in each country. Knowing qualitative and quantitative problems in water resources monitoring systems is one of the most important steps in water resources system management and pollution reduction plan. Recent studies in the field of water quality monitoring network has showen the needs for more researches, despite the abilities and investments in this field. One of the most important problems is the difference between required data and provided data in monitoring networks. So, monitoring systems should be revised and modified in several cases. High monitoring expenses necessitates optimizing monitoring systems to prevent cost loss. Being aware of network properties is an essential step in evaluating existing quality monitoring network. Locations of sampling stations, time frequencies, qualitative variables specifications and sampling duration should be considered in these evaluations.Reduce the cost of monitoring networks and maximize the obtained information, is the common objectives of the monitoring networks planning. From a monitoring perspective, identification of the reservoir eutrophication situation is of particular importance. Eutrophication phenomenon affects water quality strongly and causes serious limitations on the water utilization ability. Autotrophic organisms and algae overgrowth increased turbidity, toxic substances, increased sedimentation rate, oxygen concentration in the middle of the day and reduced severely by decreasing sunlight from sunset until next day morning, which causes anaerobic regions creation in deeper areas of the reservoir as the result.In this study, locations of Karkheh dam reservoir that there was maximum variations in quality indices values using CE-QUAL-W2 model, was identified. PO_4, NO_3, chlorophyll A and dissolved oxygen was studied to eutrophication control in reservoir. Because of limited available data from the time frequencies and sampling location point of view, dam reservoir was modeled by CE-QUAL-W2, 2D qualitative model for a period of one year. Using time series developed in previous step in model cells, time variance of studied parameters in the entire model cells was calculated and was used as a measure of its value change during time. Critical path from monitoring point of view was obtained after fitting best curve to cells with maximum time variance for studied qualitative indices. Placement of monitoring stations on this route will get the maximum information about the quality of the monitoring operation. The results showed that the proposed methodology is efficient in determination of critical paths for quality indices from monitoring perspective, in the dam reservoirs. ...Being aware of network properties is an essential step in evaluating existing quality monitoring network. Locations of sampling stations, time frequencies, qualitative variables specifications and sampling duration should be considered in these evaluations.Reduce the cost of monitoring networks and maximize the obtained information, is the common objectives of the monitoring networks planning. From a monitoring perspective, identification of the reservoir eutrophication situation is of particular importance. Eutrophication phenomenon affects water