فصلنامه حفاظت منابع آب و خاک
سال سوم شماره 1 (پیاپی 9، پاییز 1392)

Invert traps are one of the most effective methods for separating and collecting sediments in open channels. In this research، some experiments were performed in a channel with 4 m long and 25 cm wide for 13 different invert trap configurations with different inlet and outlet angles. To determine the best trap geometry that has the most retention ratios، four types of plastic beads as a laboratory sediments with the same density but different size and apparent weight were tested in a constant time. Results showed that the inlet and outlet angles of the trap، has a considerable impact on the amount of deposited sediments. In the case of vertical walls of the entrance، whatever outlet wall of the trap has milder angle، trapping rate was larger the incoming angle of the trap was smooth and the outlet wall is vertical، although sediments could easily sinked in، but due to strong vortices formed downstream of the trap، much of these sediments re-suspended and directed away from the trap. Quantitative analysis of the results showed that from the 13 tested geometries، trap with inlet angle of 90° and 34° as an outlet angle، has the highest efficiency on trapping the sediments.

Coastal aquifers have a high potential for contamination by seawater intrusion. Thus، the vulnerability of groundwater resources can be very effective in identifying vulnerabilities and sensitive groundwater aquifers. This study was conducted to evaluate Kish island aquifer vulnerability. The DRASTIC model was employed and modified based on the coastal aquifer conditions. Two additional parameters were included to the model which describes the balance between seawater and aquifer water level. The vulnerability maps were produced by DRASTIC and M-DRASTIC models. The comparison of these maps was performed using EC and TDS as the main indicators. The required data were collected from the existing reports as well as some extra direct water sample measurements. The overlaying of the vulnerability map was obtained by the DRASTIC method. Comparison of M-DRASTIC with EC and TDS maps showed that the mean differences for DRASTIC map with EC map is 17. 41 and 10. 24، respectively and for M-DRASTIC is 0. 69 and 0. 55، respectively. This indicates that the M-DRASTIC model is more adapted to coastal zones. The vulnerability index in DRASTIC method is generally lower than M-DRASTIC range. Based on the M-DRASTIC vulnerability analysis، it was found that 17. 8، 48. 1 and 34. 1 percents of Kish island area is under average، high and very high risk of groundwater contamination، respectively.

At the present time، contamination of water and soil resources is an important environmental challenge. Therefore، decontamination of such soils is a prerequirement of using these resources. The stabilization/solidification is cost effective remediation method that prevents spreading of heavy metals in soil and water resources. In this process، contaminated soil reacts with amendments such as phosphate materials to form low soluble or non-soluble stable materials. In this research the performance of dicalcium phosphate (DCP) in stabilizing and immobilizing of two ubiquitous metals Cd and Cu through soil was investigated. To understand the mobility of these metals within coarse textured soil، 12 leaching column tests were conducted. Four soil samples were contaminated with 500 mg/kg Cu while four others were contaminated by 500 mg/kg Cd. One of the specimens was left blank، while the other three were mixed with 0. 1، 0. 2 and 0. 5% (by weight) DCP stabilizer. In addition، four other samples were simultaneously contaminated with both metals and the same amount of additive. The results indicated in the case of Cu contaminated samples، application of 0. 1% DCP reduces 93% of this metal in the first pore volume of effluent. For Cd، this amount was 80%. Increasing in the amount of stabilizer (0. 2 and 0. 5%) neglects the metal in effluent. In simultaneous contamination using 0. 1% DCP، 90 and 92% of Cu and Cd was reduced، respectively. Therefore، immobilizing of Cd performed better than Cu when both were present. This study shows that DCP is an effective additive for stabilizing Cd and Cu to protect groundwater from contamination leached out of polluted coarse textured soil.

Proper management of saline and sodic soils is essential for optimal conservation of soil and water resources. Accumulation of soluble salts within the root zone is one of the major problems in arid and semi-arid regions. To overcome this problem، leaching of accumulated salts from such soils is necessary. The most important task in leaching practices is assessment of water quantity required for leaching of saline and saline-sodic soils. Therefore، reliable estimation of the required leaching water quantity is vital for reducing soil salinity to a desirable level. The objectives of this study were to introduce an empirical model to account for reclamation water and to compare the obtained results with some available models. Consequently، a large scale field experiment was conducted in jofeir region at south part of west Khuzestan plains، covering an area of 21285 ha with S3A2 salinity-sodicity classes. The intermittent pounding experiment was conducted with six double ring infiltrometers in a circular array. All experiments were accomplished by applying 100 cm of water in four-25 cm intervals. The leaching water was supplied from Karun rive. Four mathematical models were applied to the collected experimental data to derive a suitable empirical model. The results indicated that the proposed power model with maximum correlation coefficient of 0. 83 and minimum standard error of 0. 44 can provide reasonable estimates for leaching process compares to the previously proposed models. The results indicated that the empirical relations given by Rajabzadeh (2009)، Hoffman (1980) and Laffelar and Sharma (1977) can not resemble the field conditions. However، the empirical relationships introduced by Pazira and Kawachi (1981) and Revee (1957) overestimate the depth of reclamation water. The empirical models of Pazira and Keshavarz (1989)، Asadi et al.، (2013) and Dieleman (1963) underestimated the depth of required reclamation water compares to the newly proposed model.

A new approach in drainage design call for the control of shallow water table at vicinity of the crop rootzone for the purpose of proper soil and water conservation. The objective of this study was to evaluate the effect of reducing drainage depth on salinity and water rate of drains. For this purpose، R 9-11 farm with average drainage depth of 2 and distance of 60 meters and a R 8-7 farm with depth of 1. 4 and distance of 40 meters of sugarcane in south Khuzestan were selected. During the study، constructing six pisometers groups in two farms with different distances from drain collector، the daily water table level and outlet drain flow rate and the salinity of groundwater، and outlet drain in each irrigation were measured respectively. Results indicated that by increasing the irrigation water، the difference of hydraulic load between the bottom layers to the top ones in both farms، leads the vertical flow upwards. In addition، by reducing the drain insertion depth، the groundwater rate of salinity reduces، but these changes of salinity depend on the impermeable layer depth. In addition، by reducing that drain salinity was affected by irrigation water and groundwater salinity and the difference of drain insertion depths، location of impermeable layer and sand lenses affect this salinity. In addition، by reducing the drain insertion depth، outlet drain flow rate was intensively reduced such that in R 9-11 and R 8-7 farms، outlet drain reached to 3. 86 and 0. 74 L/s، respectively.

Solar radiation is one of the input parameters needed for simulation of processes associated with climate changes، hydrology and ecology. Proposed models to estimate this parameter because using the weather data from a spatial point، would also provide point estimations. In this study، two experimental models including Hargreaves - Samani and Mahmood - Hubbard that are based on air temperature data، with the input data of daily LST products MOD11A1 and MYD11A1 MODIS instead of air temperature، were used to estimate the solar radiation. The real data were obtained from Ahwaz synoptic station for 2006 and 2007. Validation results indicated that Hargreaves - Samani input MOD11A1 LST product and the model of Mahmood - Hubbard MYD11A1 products with input LST (Land Surface Temperature) have the larger and lowest accuracies in estimating solar radiation. Validation results were further indicated that Hargreaves - Samani input MOD11A1 LST product and the Mahmood - Hubbard input MYD11A1 LST product، respectively، have maximum and minimum accuracy in estimating solar radiation. For these models، R2 and RMSE statistics were، respectively 0. 83، 2. 46 (mj m-2 d-1)، 0. 79 and 4. 09 (mj m-2 d-1). The Hargreaves -Samani model by using M5 model tree models (RS-M5-1 and RS-M5-2) based on LST data of MOD11A1 MODIS products geographic variables were formulated and the outcomes were compared with results of experimental models. The results showed that compares Tree Model RS-M5-1 and experimental models with the same input، The M5 tree model has higher accuracy. In general، tree model RS-M5-2 with LST products MOD11A1 inputs، can estimate the maximum and actual sundial and extraterrestrial radiation more accurate than other models. For this model، the values of R2 and NSE were estimated to be 0. 87 and 0. 86، respectively. The root mean square error for this was 10. 24 percent.