Evaluation of management practices on agricultural nonpoint source pollution discharges into the rivers under climate change effects.

In recent years, agricultural non-point source pollution (ANPSP) has become the biggest threat to Aras River water quality by completing the Mughan irrigation and drainage network. Nutrient pollutants, including nitrate and phosphate, released into the river through drains have created a range of obstacles for locals living around the river. Agricultural activities are generally considered the largest source of non-point pollution. They have no complex and uniform impact along the river. Thus, the spatial distribution of ANPS and highly polluted areas should be identified to manage watershed management. This study proposes a simple framework for identifying pollutant-sensitive areas along the river and management strategies to improve water quality. To this aim, the main factors affecting ANPSP were identified, and the effectiveness of the scenarios selected to comply with water quality regulations for drinking and environment during 1993-2007 were simulated. Based on the sensitivity analysis, land use and fertilizer are the main factors affecting river ANPSP. Thus, their changes were modeled in different scenarios. Based on the results, the ANPSP load was higher downstream. The agricultural lands in region 3 were considered the main source of pollution. Comparing the management scenarios showed that the amount of nitrate and phosphate leaching into the river decreased to 18.1 and 8.35 %, respectively, by reducing the consumption of urea and phosphate fertilizers by 50 %. The results help watershed managers implement eco-friendly land use and nutrient management programs at specific locations during specific periods to control ANPSP along the rivers.

Risk and damage-based optimal design of storm sewer networks using rational and fully dynamic methods, a case study (Tehran region 2).

In this study, the risk analysis is used to determine the return period in which the design cost plus the damage risk cost is minimum. The damage includes the roads and traffic, the lawn areas, and the residential and commercial buildings. The traffic damage is based on two factors, time of delay and social negative impacts. The nonlinear reservoir model is used to convert the rainfall into runoff and the dynamic wave model is utilized to perform the network hydraulic simulation in stormwater management model (SWMM) software. This model is defined as an appropriate model. This model was applied in the risk analysis of a region in Tehran to obtain the optimal return period design. The results indicated that the optimal return period is 10 years. The rational method was also applied to the same region and same return period, but the total design cost of the rational method was greater by 5%. The damage due to the traffic include financial damages due to delays and loss of fuel resources in addition to the dissatisfaction of people due to the psychological burden.

Simulating the effects of low impact development approaches on urban flooding: a case study from Tehran, Iran.

Low impact development (LID) methods have been shown to be efficient in reducing the peak flow and total volume of urban stormwater, which is a top priority for effective urban stormwater management in many municipalities. However, decision-makers need information on the effects of LIDs and their associated costs before allocating limited resources. In this study, the Storm Water Management Model (SWMM) was used to investigate the effects of five different LID scenarios on urban flooding in a district in Tehran, Iran. The LID scenarios included rain barrel (RB) at two sizes, bio-retention cell (BRC), and combinations of the two structures. The results showed that significant node flooding and overflow volume would occur in the study area under the existing conditions, especially for rainfall events with longer return periods. BRC and combinations of BRC and RBs were the most effective options in reducing flooding, while the smaller-size RB was the cheapest alternative. However, normalized cost, obtained through dividing the total cost by the percent reduction in node flooding and/or overflow volume, was smallest for BRC. The results of this study demonstrate how hydraulic modeling can be combined with economic analysis to identify the most efficient and affordable LID practices for urban areas.