Adaptive Survivability-based Approach to Assess the Health Condition of the Rivers Receiving Wastewaters, Using SOD Rate and Its Associated Parameters(Case study: Karkheh River, Target Zones beside the Pay-e-Pol Plains, SW-Iran)

As the veins of the Earth, Rivers have a determinative role in regulating the functional behaviors of their linked ecosystems and supporting human life. This research was conducted to address the major issue to assess the river's health and survival condition alongside its vulnerability potential, using a benthic-based sustainability index. For this purpose, river-bed sediment oxygen demand (SOD) rate and its associated factors, including Texture, fine-PSD, Nutrients (TOM), besides some basic field parameters of river-water were measured. All required samples were collected from 9 sampling points located on the target zones of Karkheh River in due course. SOD data with regard to related factors were calculated and analyzed. The rates of SOD ranged from 0.71 to 1.74 g O2/m2/day. Further, this index was classified in varied quality domains. Afterward, a predictive equation was determined among SOD rate and its associated parameters using MATLAB software. Finally, the results revealed that the river health suitability in the research area is in categories moderately clean and slightly degraded during the study period. Additionally, the increase in TOM concentrations, together with a decrease in sediment particle size, led to an increase in SOD-rate accordingly. The source pollution load reduction rate under the optimal suites of BMPs in the range of 15 to 66 percent was also one of the outputs of this research.  In conclusion, the consequences of this study can be used as a rapid diagnostic tool to support regional water authorities and other stakeholders to promote the best practices for protecting the health condition of the riverine system, focusing on selecting the appropriate discharge points along the receiving watercourse and on effectively managing the drain-waters/effluents.