JOURNAL OF WATER AND SOIL RESOURCES CONSERVATION
Year:2014 | Volume:3 | Issue:3|Papers Count:6

An experimental study was conducted to investigate the effect of blocks distance from the sluice gate on hydraulic jump characteristics. A number of 36 tests in a range of Froude numbers, relative tailwater depths and blocks distances from the gate were considered. Dimensional analysis was used to interpret the results and the effect of each parameter. The obtained results showed that the blocks distance from the gate has negligible influence on energy dissipation and also on relative energy dissipation. Increasing in Froude numbers from 6.4 to 8 resulted in increasing the relative energy dissipation nearly 8%. However, once relative tailwater depths increased from 5.26 to 7.36, the energy dissipation was considerably decreased, i.e. about 34%. Results of energy dissipation efficiency showed that the blocks distance from a gate has no clear effect on this parameter, but it was decreased with increasing Froude number and decreasing relative tailwater depth. Furthermore, the results showed that the relative jump length was increased about 115% when the relative blocks distance increased from 0.18 to 0.54.

Soil erosion is one of the major worldwide environmental challenges and its related destructive effects cannot be ignored at both inside and outside of a region. Splash and transport of soil particles by raindrops are the initiating mechanisms of water erosion. The objective of this research was to investigate temporal variations of splash erosion in different slopes and land uses using a rainfall simulator. The experiment was conducted as factorial based on completely randomized design with three replicates. The experimental treatments were consist of slope at two levels (5 and 15%), duration of rainfall at four levels (5, 10, 15 and 20 minute) and different land uses (forest and agriculture).The results indicated that amount of splash increased with increasing rainfall duration. The amount of splash erosion of the 20-min rainfall duration was 2.08, 1.76 and 1.08 times more than of 5, 10 and 15-min, respectively. The average soil loss by splash erosion in agricultual and forest land uses was 29.37 and 25.56g.m-2, respectively. Furthermore, the results showed that as slope increased from 5 to 15% the amount of splash erosion increased 11%. In general, at all rainfall durations, splash erosion increased significantly with changes in slope steepness (from 5 to 15%) and land use from forest to agriculture, but there was no significant difference between the15 and 20-min rainfall durations.

Soil hydraulic properties are very important in hydrological cycle. The objective of this study was to explore the feasibility of estimating soil hydraulic parameters using diffused spectral reflectance data in visible, near-infrared and short-wave infra-red (350-2500 nm) ranges. Consequently, hyper-spectral reflectance of some soil samples was measured using a handheld spectroradiometer. After preprocessing the spectra, correlation between spectral data in each wavelength and Mualem van Genuchten hydraulic parameters (a*, n and Ks*) were explored. Using stepwise multiple regression method, parametric spectro-transfer functions (PSTFs) were derived. According to the results, the largest correlation coefficients were obtained for a* and n at wavelengths 550 and 2300 nm, while Ks* parameter showed maximum correlation at wavelength 1927 nm. The parametric STFs showed similar results for a* (R=0.54) and n (R=0.58). The best results were obtained for Ks* parameter with R values equal to 0.76. The parametric STFs provided mean RMSR values of 0.017 cm3 cm-3 for all the pressure heads. Although the performance for MvG parameters was not very high, this approach can be considered as a novel application of soil spectroscopy and might be used as a useful indirect method for estimating soil hydraulic properties.

Conservation of soil and water resourcesis the most importantce factor in protection of ecosystem and agricultural product. Due to limited soil and water resources, methods that can optimize the use of water and fertilizer in tea farms are very important. In this study, to analyze theeconomic productivity of water and nitrogen fertilizer in supplemental irrigation in tea farms, split plot experiment, with six levels of 0, 100, 200, 300, 400 and 500 kg N ha-1 (N0 to N5) and five irrigation levels consisting of full irrigation (I4), deficit irrigation (I1, I2, I3) and no-irrigation (I0) in four replicates (2008-2010) were conducted. The Results indicated that the highest economic productivity of water and nitrogen fertilizer is obtained with supplemental sprinkler irrigation (3424 m3) and 200 kg N ha-1 application. Increase or decrease in the amount of nitrogen recommended in full irrigated, reduce economic productivity of water and fertilizer. The best economic productivity of water and fertilizer in deficit irrigation was obtained with application of 200 and 100 kg N ha-1, respectively. In rainfed or no irrigation condition, application of 100 kg N ha-1 can be recommended to achieve maximum economic productivity in tea farms.

Increasing population and water demands caused a considrable challenge for decision makers in water sector. Also climate change in near future will exacerbate the situation. This study evaluated the impacts of climate change on water supply reliability and allocation in Karkheh river basin. In this study for assessing the effects of climate change on Karkheh river basin water supply, 15 GCMs and several greenhouse gas emission scenarios were applied to evaluate the changes of precipitation and temperature for time horizon 2050s. Then multiple river flow time series (RFTS) were generated by feeding future temperature and precipitation into a calibrated rainfall-runoff model. Due to the uncertainty of GCMs for generating future temperature and precipitation, the forecasted river flow for mid-century had a wide range of changes between -50% to +36%. Therefore for dealing with uncertainty of GCMs, the hierarchical clustering method was used to identity 5 clusters from 35 RFTS and subsequently 1 representative member from each clusters. Also three management strategies of crop pattern change, increasing irrigation efficiency and water reuse for adaptation of climate change was evaluated. Results showed that building new dams in upstream will decrease the reliability of agriculture water supply to less than 70%. Also, the water reuse with more than 90% reliability, is the most effective strategy for dealing with climate change. The crop pattern change includes comparable water demand reliability, but less costs. However, execution of crop pattern change is a low-cost strategy, depending on farmers cooperation.

Data acquisition on effects of type, amount and transportation processes of sediment load at different temporal and spatial scales due to sand mining activities is essential for proper and better management of sand harvesting. Nevertheless, different aspects of effects of sand mining activities on sediment load changeability at different temporal and spatial scales have been less considered. The present research has been therefore formulated to investigate the effect of sand and gravel mining activities of three mines located on Mazandaran Province viz. Vaz-e-Oulia mine with light and traditional harvesting, Vaz-e-Sofla mine with semi-heavy harvesting and Alesh-Roud mine with intensive harvesting by heavy machinery on suspended sediment concentration load. Toward this attempt, the suspended sediment samples were collected on monthly basis and simultaneously from upstream and downstream of sand and gravel mines from February 2012 to January 2013. The results indicated that the suspended sediment concentration increased at the period of sand and gravel mining activity. It was observed that the suspended sediment concentration in upstream of Vaz-e-Oulia mine increased in June, December, February and March with 40, 5, 23 and 75 percent, respectively. According to the results, the rate of suspended sediment concentration in upstream of Vaz-e-Sofla mine compared to downstream of Vaze-Sofla mine also increased in April, August and February with respective rate of 2, 12 and 36 percent. In addition, the rate of suspended sediment concentration in upstream of Alesh-Roud mine compared to downstream of the study mine increased in May, June and March at tune of 71, 50 and 94 percent. A limited local effect and at a maximum range of a few hundred meters on suspended sediment concentration and in coincidence with harvesting time was also confirmed.