مجله سامانه های سطوح آبگیر باران
سال هشتم شماره 4 (پیاپی 27، زمستان 1399)

Knowing how the low flow changes upstream and its trend provides valuable information on water resources management, water rights, and the improvement of crop patterns. It also helps to identify suitable areas for water control management along the river from water resources management perspective. In addition to economic issues, the preservation of river ecosystems is an important matter that has not received much attention so far. The 60-day low flow time of occurrence differs between upstream and downstream. The spatial trend of discharge also varies from upstream to downstream. In this study, some hydrometric stations of the Karkheh basin were investigated, and after data analysis, annual 60-day time series of low flow in each station were extracted. The average annual discharge was also calculated and the ratio of 60-day low flow to mean annual discharge was obtained and it was used as an evaluation index. Multivariable regression between the above indices and 60-day low flow were established with effective morphometric parameters. The results showed that the 60-day low flow had a significant correlation with the basin area (R2=0.8), and the distance of each station to the output of the Karkheh basin (R2=0.2) had the most correlation with the flow indices. On the other hand, in the upstream, the ratio of low flow to mean annual discharge was lower than the downstream flow, and the indices increased towards the outlet of the basin. Therefore, more attention should be paid to rainwater harvesting methods to manage water resources in the upstream basins.

Small sediment dams are the key structures for controlling sediment flow and improving the course of waterways in watersheds. In Kermanshah province, the efficiency of these structures in sediment accumulation has been less studied and evaluated. This study aimed to investigate the efficiency of these structures in sediment retention and flood control in three watersheds of the province. For this purpose, while selecting three study basins in the East (Hajiabad basin), North (Razin basin), and South of the province (Mereg basin), the target dams for the study were identified. A total of 30, 14, and four dams were gabion, dry-stone wall, cement-masonry, respectively. Then, the accumulated sediments in the tank behind the dams were examined with the help of surveying and sampling from different sections. Examination of the results in the Hajiabad basin in the East of the province, which was the main cause of erosion showed that gabion and dry-stone wall construction have been able to reduce soil erosion and sedimentation by 13%. In the Razin watershed in the North of the province, cement-masonry and gabion dams had managed to trap about 886 tons of sediment. In the Mereg watershed, the results showed that the upstream dams with 9245 kg/ha had the highest and the downstream dams with 3575 kg/ha had the lowest sediment control performance. The results of this study showed that in basins with high sedimentation capacity, dry-stone wall dams are one of the most important low-cost structures to prevent sediment transport, especially coarse particles. However, the construction of dams with low drainage to prevent the transfer of fine particles is also effective.

Due to the undeniable impact of drought on human life, careful study of this phenomenon seems essential. The purpose of this study is to evaluate the accuracy of Geostatistical methods in preparing the drought severity map in the Malayer plain using the Standardized Water-Level Index (SWI) and analyze the trend of the Piezometric well. The results based on RMSE and MAE criteria showed that among the interpolation methods, simple Kriging method (SK) with the spherical model due to having lower RMSE and MAE (for 1999 with RMSE = 0.05 and MAE = 0.001 and For 2012, with RMSE = 1.04 and MAE = - 0.0004) was the most accurate method and was selected as the most appropriate approach to prepare the drought severity map. The results also showed that in most Piezometric wells in the region, the trend of water table level drop is significant.

Due to climate change and changes in plant water needs, it is necessary to evaluate climate change in the coming decades with the aim of appropriate environmental planning to adapt to future climate conditions. The main factor of water resource consumption in arid and semi-arid regions is agriculture and consequently evapotranspiration, so knowledge of the change and its prediction plays an effective role in the planning, development, and management of water resources. The present study uses the Lars WG Model. Using this model, the temperature in three time periods (2011-2030, 2046-65, and 2081-2100) with four general atmospheric circulation models (IPCM, INCM3, HADCM3, and NCCCSM) in three different scenarios (world with sustainable development, rich world, and the isolated world) has been calculated, then the evapotranspiration changes were examined in the Southeast of the country in the three mentioned periods for eight stations. For this purpose, the Thornthwaite equation was used to calculate evapotranspiration. The results show an increasing trend of temperature followed by an increase in evapotranspiration in the coming period. The average increase in evapotranspiration in the NB1 model is less than other models and has the lowest value and the highest value in Kerman and Iranshahr, respectively. The relative changes of evapotranspiration until 2099 in Kerman and Iranshahr stations are 10.692 (mm / day) and 23.194 (mm / day), respectively

Performance and control are two important components in any executive activity and their purposes are to correct and improve the functions and reduce wasting resources for better productivity and adoption of appropriate techniques that ultimately lead to the development of programs. Therefore, the present study aimed to simulate underground water flow and investigate the effects of artificial water supply projects on the underground water resources of Frizi plain in Chenaran using a mathematical model and MODFLOW code. The studied aquifer model is the most sensitive to changes in hydraulic conductivity and discharge of wells and shows less sensitivity to changes in surface water supply due to rainfall. The artificial water supply scheme of Jamab in the control scenario had caused an annual increase of 453717.6 meters2 of water to the aquifer. The maximum volume of water entering the aquifer system through the artificial water supply of Jamab in 1995-2012 was equal to 1.8 million cubic meters, and according to the control scenario had increased by 1.35 million cubic meters, this amount of supply had increased the average of the water level of the aquifer of Frizi plain compared to the control scenario in the forecast period in 2014, 2015, and 2016 by 0.09, 0.11 and 0.17 m, respectively. The minimum volume of water entering the aquifer through the artificial supply of Jamab in 1995-2012 was in 1995 and 2002, which was approximately equal to 170 thousand cubic meters, which compared to the control scenario had decreased by 283 thousand cubic meters, the estimated revenue in the system obtained during the operation period until 2012 and was equal to 57.5 billion tomans. The profit to cost ratio of the project in terms of all revenues from project ecosystem functions and production was about eleven, which showed that the project was profitable until 2012.

Rainfall and runoff estimation play a fundamental and effective role in the management and proper operation of the watershed, dams and reservoirs management, minimizing the damage caused by floods and droughts, and water resources management. The optimal performance of intelligent models has increased their use to predict various hydrological phenomena. Therefore, in this study, two intelligent models including, genetic programming and support vector machine were used to forecast the monthly precipitation of Ardabil province. For this purpose, precipitation, temperature, and relative humidity on a monthly scale were considered as the input parameters of the models. The results showed that the performances of both models were good and almost the same (mean absolute error of 0.8 and 0.721, respectively), but according to the evaluations, the support vector regression model had a relatively better performance (correlation coefficient 0.999) compared to another model. In general, it can be concluded that the support vector regression model has been more suitable for modeling and forecasting monthly precipitation in Ardabil province.