Journal of Water Resources Engineering
Year:2013 | Volume:6 | Issue:18|Papers Count:8

Check dams are one of the most common alternatives for reducing watershed’s sediment production, controlling erosion, stabilizing stream long profile and recharging water tables. In the Fars province, 70% of recent watershed measures for erosion and flood control consist of check dams. Considering that the function of check dams is related to environmental condition, therefore it may not be vise to judge about their function only on the basis of limited observations. So, this research has been carried out to determine the technical function of check dams in Fars province. In this research, 1056 check dams were investigated in Tavileh-Band watershed located in Eqlid, Tange-Shoul watershed located in Marvdasht and Jonagan watershed located in Mamasani of Fars province, and the capacity of check dams sedimentation and the volume of deposited sediments by existing check dams was determined by measuring and empirical methods. Meanwhile, sediment calculation was carried out by MPSIAC method. The results of the analyses and comparison of the amount of settled sediment with the amount of total generated sediment in each watershed indicated that, within 10 years, considerable amount of sediment were trapped behind the check dams at Eghlid and Marvdasht region. But because the check dams were damaged, part or all of the trapped sediment gradually escaped. Not repairing the damaged check dams allows the sediment to gradually tranport out of the watershed. Apart from the partial destruction of check dams, due to neglecting technical points in the construction of check dams such as choosing improper abutments of check dams or optimum parameters like the distance between the check dams in each channel system, the whole sedimentation capacity of check dams is not applied. At Mamasani region due to the perfect construction of the check dams and their stability, it’s hopefully expected that in the following years much more sediment will be controlled, provided that the check dams are preserved well. According to the analyses, if all the steps of a watershed project including study, execution and maintenance management were carried out properly, it can be concluded that check dams will be completely efficient in all aspects of erosion and sediment management.

Water resources management and its planning are increasingly impact by the climate change, especially in the arid and semi-arid area. As the tree rings integrate the effects of internal water stress, their thickness maybe correlated with the amount and distribution of precipitation during the growth period. Therefore, based on the recommendations of the world Meteorological Organization, 20 years of seasonal and annual precipitation were collected from the Mashhad Synoptic Station, and correlated with the growth rings of beech (Fagus Orientalis Lipsky), poplar (Popolus) and willow (Salix). These trees were irrigated solely by precipitation. Four indices, namely, rainfall anomaly index (RAI), Standard Precipitation index (SPI), percent of normal precipitation index (PNPI), and Z score were evaluated to find the best fit between the growth ring thickness and the seasonal and annual precipitation. On the seasonal scale, the number of drought indicators was relatively the same for all of them except the RAI; however, they were different using the PNPI. Apparently, the PNPI is not a good indicator in the annual estimations; lengthening the precipitation duration decreases its prediction rigorousness. The result was a high correlation between drought indices and the growth ring thickness during spring and winter than in other seasons. Willow’s response to the amount of precipitation was higher than the other two trees. It should be so, as it is a phreatophyte. The results indicate clearly that there are sufficient correlations between the thickness of the growth rings and the chosen indices. All of the indices indicated the occurrence of about eight drought periods with various degrees of sensitivity. The SPI proved to be the weakest drought indicator in the group, as it showed the least sensitivity to the occurrence of droughts; tree rings increased their thickness when the SPI indicated the presence of a drought.

In recent years, the fuzzy-logic-based methods have been developed to consider the intrinsic uncertainty in environmental problems. Noting that the inappropriate classifications that traditional methods apply to develop an index, we intend to develop a better index that measures the river water quality based on the fuzzy logic. Using this approach enabled us to benefit from experts’ knowledge in designing the model and mitigating the shortages of previous methods. In the present study, a methodology based on the Fuzzy Inference Model to assess the river’s water quality is used. The potential application of the fuzzy model has been tested with a case study for the Karoon River. Therefore, a data set collected from 2008 to 2009 from seventeen hydrometric stations along the Karoon River has been used. The most important parameters that affect the water quality namely DO, BOD5, NO3-, Cl-, and EC has been used. Finally, using the Fuzzy Inference Model, the Karoon River’s water quality was classified in three categories: good, moderate and poor. Results of the present study suggest that the fuzzy inference model can be considered as a comprehensive approach for assessing the river water quality in different seasons. Therefore, this methodology offers a suitable and alternative tool to be used in developing effective water management plans.

Nowadays the quality of surface water is a serious matter of concern to water authorities. Certain human activities, as well as some natural processes, contaminate surface water resources and decline their quality for drinking, industrial, and agricultural uses. Planning for preparing a reliable guideline for evaluation of water quality is not possible without understanding the spatio-temporal variations of stream water. In this study, spatio-temporal variations of 12 water quality parameters: total dissolved solids (TDS), electrical Conductivity (EC), acidity (pH), cations (Ca, Mg, Na and K), anions (HCO3, CL and SO4), sodium absorption ratio (SAR) and total hardness (TH) were investigated at six stations in the Talar Watershed during the 1382 - 1390 study period at the significant level of 0.01<P£0.05, 0.01<P£0.01 and P£0.01. The results showed that sampling time had a significant impact on the variations of the quality parameters and this impact varied spatially. Temporal variations at the Kiakola, Pol Shahpoor and Shirgah-Talar Stations were not significant; however, time had a meaningful impact including increasing the amount of most water quality parameters (decline in river water quality) at the Polsefid-Talar, Khatirkuh-Doab and Paland Stations. Moreover, spatial variations analysis revealed that space had a significant impact on the change in the quality parameters of the water as well. Therefore, Khatirkuh-Doaband and Pool Shahpoor Stations had the best and the least water quality, respectively.

As furrow irrigation is practiced on a large percentage of farm fields in Iran, the design and operation of this system calls for improvement. As collecting the necessary data to predict of advance and recession curves in a furrow requires field accurate measurements. These operations are costly and time consuming and the use of approved models is advantageous. The main objective of this study was evaluating the hydrodynamic, zero inertia, and kinematic wave models prediction by field observation using the SIRMOD software. Sensitivity analysis for this software was performed by employing three input parameters: discharge, Manning’s roughness coefficient and furrow slope. Field experiment performed at the Research Farm of Faculty of Water Sciences Engineering, the Shahid Chamran University of Ahvaz. Data were collected from three furrows, 60, 80 and 90 meters long, with three replications and three discharges of 1.0, 1.25 and 1.5 liters. sec-1. Four indices: 45 degree line (a), model average prediction error (Er), regression coefficient (R2) and average relative error of model (Ea) were used to evaluate the model’s predictions. The results of sensitivity analysis indicated that the SIRMOD software was sensitive to variations of input parameters. The predicted values of advance phase for all models were more than the observed values, but, generally, the amounts of (a) and R2 indicated that the hydrodynamic and zero inertia models had better performance in prediction of advance phase compared with the kinematic wave model. Moreover, the hydrodynamic and zero inertia models, as in the advance phase, predicted the regression phase better compared with the kinematic wave model.

Installation of inflatable dams where previously small concrete dams used to be constructed is among the environmental solutions adhered to in recent years. An inflatable dam is a thick synthetic tube, which is usually installed across a river, and confronts the flow by being filled or emptied with air or water, to an arbitrary height. Inflatable dams may contain a deflector or lack it. As the foundation invert elevation affects the dam’s performance, it may be placed at different elevations relative to the streambed. A stilling basin is formed when the invert is lower than the streambed; otherwise, the invert basin, maybe flush with the streambed. Hydraulic parameters such as the flow rate, the depth of water on the upstream and the downstream of a dam, and the depth before and after hydraulic jump were measured and the flow energy loss over the dam was computed. A decreasing trend in the relative energy loss with an increase in the drop number was observed.

In terms of the nature of flow profile over weirs, cylindrical weirs are classified as short-crested weirs. Advantages of the cylindrical weir shape include the stable overflow pattern, the ease to pass floating debris, the simplicity of design compared to the ogee crest design. In the present study, numerical simulations of overflow cylindrical weir with smooth and rough surfaces were done employing two sizes using the standard k-e turbulence model. The free surface was determined using the VOF method. Results showed that the k-e turbulence model and the VOF method for predicting of the water surface and flow discharge were suitable, and the relative error of the predicted water head and measured value were within 1-4 %. The effect of roughness in a cylindrical weir on the characteristics of flow, such as discharge coefficient, were studied and compared with the results of previous studies. Predictions according to the Dressler’s theory and the horizontal velocity distribution obtained from the flow function over a curved bed are also presented for comparison.

Watershed system configuration and conditions change as newer water supply, irrigation, industry and municipal development projects are constructed. In such a new condition, applying the current operating rules for reservoirs, aside from not being optimum, will produce different economic and social costs, too. Therefore, it is necessary to coordinate the operation in the new condition and update reservoirs operating rules. Coordinating the hydro-system operation and updating the reservoirs, operation rules at different stages of the basin development are studied in this research. Therefore, a long-term optimization model is developed, which takes into account the upstream operation impacts on the downstream performance, and coordinates operation of different hydro-system components in a manner to maximize satisfaction of different stakeholders’ targets as much as possible. Application of the model to the Karkheh’s hydro-system analysis at different development stages for an assessment of coordination and updating of operation impacts shows that after construction of the Karkheh, Saymareh and Sazbon Dams, 60% of water demand targets will not be met in comparison with the updated rule curves application if the primary rule curves of dams that are determined for each dam are used individually in practice. Besides, non- coordination of the Karkheh’s hydro-system operation and updating reservoirs operation rules will reduce water supply reliability by 50% in a 20 year planning horizon in comparison with a coordinated and updated operation of the Karkheh’s hydro-system.