Iranian Water Research Journal

Abstract Time parameters are used in the majority of hydraulic and hydrologic models. The most popular time parameter in hydrology is Time of Concentration (TC). TC is the time that water needs to reach to outlet from the furthest point of basin. TC is used in the design of weirs, flood volume evaluation, flood hydrograph and many other hydrological analysis. There are a lot of methods for TC evaluation and this research tries to select the best method of TC evaluation in Maime basin. For evaluation of real TC, field method was applied using a salt solution for measurement of Travel Time, after that the result of it was compared with the results of empirical formula it was confirmed that Kirpich, Chow and Rational Hydrograph methods had the least discrepancy, therefore they are acceptable.

Abstract At present nitrate contamination of groundwater is a significant problem. In the past decades, nitrogen fertilizers have been widely used without considering negative impacts on the soil and ecology. The nitrate easily reaches the surface and subsurface water. The objective of this study was to investigate nitrate contaminant distribution using Geographical Information System (GIS). Accordingly, 10 observation wells were selected out of 500 operational wells and water sample collected during (12 months) of July 2007 to June 2008. In total, 120 water samples were analyzed for nitrate concentration. The results show that nitrate concentration in the central parts of the plain is lower than northern and southern parts and did not change during the year. The most contaminated region of the aquifer is located in the southern part where it is contaminated by the urban wastewater wells in the vicinity of the aquifer. In the summer, the nitrate concentration is increased due to high agricultural activities and consumption of nitrogen fertilizers. The results indicate that the nitrate leachs during irrigation and so it affects the water quality.

Abstract Theta Probe is one of the new methods for measuring soil water content. Rapid measurement, high precision and direct measurement in field condition are important advantages of this method. In this study, the effects of soil texture and compaction on water content measurement precision by Theta Probe (model ML2) were evaluated. For this purpose, three types of soil (sandy, loam and clay) were selected. Subsequently, 17 samples, from each type of soils, with various compaction and moisture content (between dry soils to saturated soil) were taken. Then, the Theta Probe was calibrated for each soil by linear and nonlinear techniques. Results of Theta Probe method compared with usual gravimetric method. The results indicated that ML2 Theta Probe have the highest precision (RMSE=% 2.7) in the sandy soil and precision of the Theta Probe have inverse relationship with clay content. Also, results showed that the effect of soil compaction on Theta Probe precision is very low and this effect increases by increasing in clay content. The correlation curves between results of Theta Probe method and gravimetric method showed the highest correlation (R² =0.95) in sandy soil and the lowest correlation (R² =0.91) in clay soil, Loamy soil had intermediate condition (R² =0.93).

Abstract In this study, the effects of sharp-crested sill on the characteristics of hydraulic jump formed in a gradually expanding stilling basin of rectangular cross section was investigated. The expansion of the basin is accomplished by increasing the bed width in the stream-wise direction. A total number of 228 tests were carried out for the range of initial Froude number from 3.1 to 10.3. Sills with various heights and different locations, relative to the jump toe, were installed in the basins with the diverging angles of 3, 5, and 9 degree. In all tests, the main characteristics of hydraulic jump including sequent depth ratio, relative length of jump and the relative energy loss were measured. The results indicate that installing sharp-crested sills have insignificant effect on the sequent depth ratio but may considerably decrease the length of jump. In addition, observations indicate that sills may improve general conditions and features of gradually expanding hydraulic jump in a rectangular channel

Abstract Limited water resources for agricultural use and poor performance of irrigation networks require optimal water consumption by application of improved control systems. Fuzzy theory has been widely and successfully applied in several engineering control problems. In this research fuzzy theory has been applied for control of water levels in irrigation canals. Using the ICSS hydrodynamic model, the fuzzy developed model is tested in E1-R1 canal of Dez Irrigation network. The performance of fuzzy control system is evaluated using several criteria such as, maximum absolute error, cumulative absolute error, and response time. Flow, depth, and gate opening variations in time are depicted and analyzed as well. The results show that average and maximum depth deviation were in the range of 0.017% to 0.143% and 0.667% to 1.222%, respectively. The maximum response time for water depth to be stabilized within 1% range of target depth was 6.6 minutes. Considering high flow variations in the canal, the results indicate that the developed fuzzy control system is successful in water depth control of irrigation canals.

Abstract In Lalejin, Ghahavand-Famenin and Chardoli areas located in the north of Hamedan province, some of agricultural water wells produce gas and their equipments are corrodes in a short period, so the farmers are incurring a large financial loss. Therefore, recognition of sources and effective factors of corrosion are important. For this purpose, using G.P.S, thermometer and questionnaires, temperature, depth of wells, period of corrosion and Geographical characteristics of 36 rings gaseous wells were recorded. Furthermore, 16 water samples from the wells were analyzed in the laboratory. Then, the amount of free carbon dioxide was estimated using Standard Nomographs. Also, data of temperature, depth, free carbon dioxide and period of corrosion were evaluated by using the SPSS program. High amount of free carbon dioxide (more than 100 mg/L) and significant difference between average of water temperature in the wells show that the presence of gas in the water is the result of gaseous hydrothermal solutions with the earth internal provenance that entered into groundwater of these area. In this study, different statistical tests show that high amount of free carbon dioxide and sulfate-chloride ions, high temperature and high salinity are the effective factors of the corrosion of the wells’ equipments. Therefore, it is recommended that the metallic equipments of wells be replaced with U.P.V.C equipments.

Abstract To compare the water requirement (WR), water productivity (WP) and economical water productivity (EWP) of wheat and rapeseed in wet years in western Iran, an experiment was carried out in Sarab Changai Agriculture Research Station (Lorestan province) in 2001-2002. Statistical analysis of resulted data showed that the differences between mean WR, WP and EWP of two plants were significant (P=0.99). Mean WR (Irrigation + effective rainfall) of wheat and rapeseed were 5000 and 6590 m3 ha-1 respectively. Mean WP of wheat and rapeseed were 1.64 and 0.60 kg m-3 and their EWP were 2128 and 1508 Rials m-3 respectively. As a result cultivation of wheat (as a winter crop) is preferred to over rapeseed because of its lower WR and higher WP and EWP.

Abstract Karkhen storage dam is the largest dam of this kind in iran with a target capacity of 7.2×10 ⁹m3. It is located in North West of Khuzestan province on Karkheh River. This study was aimed at the determination of an appropriate quality index for long term monitoring of the effects of this dam on Karkha River water quality. Four sampling stations were established. Then four standard quality indices , i.e. OWQI , DSWQI, NSFWQIm and NSFWQIa were used to test water quality in a bimonthly basis. The Jil Janwick approach was used to compare data collected by the latter indices. The comparisons suggested that NSFWQIm is a more appropriate index for water quality monitoring of Kerkhen River compared to the rest of the indices