Moien Jahanthigh; Ali Najafinejad; Mansour jahantigh; Mohsen Hosseinalizadeh
Abstract
Shortage of rainfall and drought are among the factors affecting the water shortage crisis in arid regions due to the high rate of evaporation in these areas, while reducing the amount of water productivity, it reduces soil moisture. Therefore, the application of conservation methods by reducing the ...
Read More
Shortage of rainfall and drought are among the factors affecting the water shortage crisis in arid regions due to the high rate of evaporation in these areas, while reducing the amount of water productivity, it reduces soil moisture. Therefore, the application of conservation methods by reducing the rate of evaporation and maintaining soil moisture in addition to improving plant growth and yield increases water productivity. The aim of this study was investigation of the effect of sand mulch and nano-clay in buried clay pot irrigation on temperature and humidity changes in one of the wind erosion centers of Sistan region. For this purpose, wind sediments accumulated in Sistan plain as well as flood sediments of Helmand riverbed (sediments transported during floods entering from Afghanistan) were sampled. By determining the particle size of sediment samples, the largest particle size of wind sediments was separated to prepare a sandy cover using a sieve. To prepare clay nanoparticles, Flood sediments were also pulverized using ball mill by examining the particle size and determining the main elements (using the XRF method). By preparing treatments including sand cover, nano-clay and control by installing thermometers and probes at depths of 10, 30 and 50 cm Soil temperature and humidity were measured (using TDR) for a period of 186 days. Also, at the end of the test period to evaluate soil stability indices by sampling from different depths, the mean weight diameter (MWD) and geometric mean index (GMD) of aggregate diameter were measured based on dry sieving method. The results showed that there was significant different at 5% level on soil moisture and temperature distribution between treatments. In depth 10 cm, the highest amount of retained moisture were measured in sand mulch treatment (1.2 and 1.4 times retains moisture compared to nano-clay and witness treatments, respectively). The highest amount of retained moisture in depth 30 and 50 cm is related to nano-clay treatments (45 and 68% more maintain compared to sand mulch and witness treatments, respectively). The results also show that the highest and the lowest amount of soil temperature at different depths related to witness and sand mulch treatment respectively. Mulch cover by shaping temperature equilibrium in soil profiles, caused 17.2 and 33 % reduction of temperature compared to nano-clay and witness treatments. The results also showed that, there were significant differences between treatments in mean weight diameter (MWD) and geometric mean diameter (GMD) and the highest amounts of this index related to nano-clay treatment (p<0.05). Based on the results of this study, the use of sand mulch and nano-clay by reduces the temperature and improving the stability of aggregates, increases the volume of soil moisture in the subsurface layers by 30 to 45% and also increases the retention time in soil moisture and reduces irrigation frequency compared to the state without protective action in the soil. Therefore, the application of the methods used in this study, provides the required moisture to the plants to establish vegetation in the wind erosion centers of the study area.
Moien Jahanthigh; Seysd Mohmmad Tajbakhsh; Gholamreza Mirab Shabestari; Hadi Memarian
Abstract
This research was aimed to investigate Hirmand River morphology alterations through the estimation of suspended loads transported by floods. The sediment samples were collected and suspended loads were estimated. The alterations of sediment load along Sistan reach was investigated, spatially and temporally. ...
Read More
This research was aimed to investigate Hirmand River morphology alterations through the estimation of suspended loads transported by floods. The sediment samples were collected and suspended loads were estimated. The alterations of sediment load along Sistan reach was investigated, spatially and temporally. The suitable reaches for sedimentation inspected through the high resolution Satellite imageries of Spot-5 (with the spatial resolution of 2.5-5 m). Through the geo-referencing of aerial photos and satellite images in GIS environment, the changes of river width, meander angel, and sinuosity index were estimated during the last 50 years. The t-student test was employed to assess the changes of river width during time. Results showed that the average suspended sediment load of Sistan River was 32 grL-1 and approximately 7.3 million tones sediment load entered to the study reach. According to the results, the river width has been changed, significantly. The river width in 2016 has been decreased by 0.33 of that in 1965 and 73% of the river has no capacity for flow transport and shows a high density of suspended load. This study established that the hydrology parameters (sediment and flood), biologic and slope changes are the main causes of sediment load and the changes of river morphology from a disorganized sinusoidal meanders to limited meanders. During the period of 1965-2016 the pattern of flow changed from meander to the sinusoidal. The average angel of river from 287.94 changed to 295.26 degree. The average of sinusoidal index changed from 1.39 to 1.18 and the average of flooding bed width from 160.79 m changed to 41.32 m in 2016.
