Watershed Management Research
Year:2013 | Volume:26 | Issue:1 (98)|Papers Count:13

Marls in arid climates, are high erodeable regions that produce sediments. Erosional processes in marls are too active, especially in marl hillslopes, because of low amount of permeability and lack of vegetation cover. However, different erosional forms, particularly, badland erosion is one of the distinctive properties in marly lands. This research was conducted to study chemical and mineralogical properties effect on soil erosion froms in southern Guilan province. After field surveying, Soil samples taken from different erosional forms including sheet, rill, gully, badland and their parent materials. 12 samples from surface layer of each erosional form (48 samples, totally) selected. Then, chemical parameters such as, Electrical Conductivity, exchangeable and soluble cations, organic carbon, calcium carbonate, gypsum, Cation Exchangeable Capacity, and anions, were determined.8 samples from marly soils and 2 samples from parent material prepared for X-Ray tests, too. Means of chemical parameters in different erosional forms compared with Duncan test. Statistical analysis showed that amounts of Electrical Conductivity and sodium ions had significant difference between all forms of erosion. While, other parameters, have no significant difference between all erosional forms. On the other hand, these parameters haven’t important role on erosion form and severness. Furthermore, XRD patterns of the clay fraction from surface layers showed smectitic presence in gullies and badlands. Whereas, there weren’t any expansible minerals in rill and sheet erosion. With respect to statistical results and X-Ray tests, this fact concluded sodium ions and smectitic clay minerals are the most important factors that control severness and form of erosion.

Watershed management and water resources planning need to know hydrological relationships especially the data time series of annual runoff depth at the outlet of catchments. The numbers of 7 catchments were obtained to investigate the ability of selected mathematical model for simulation annual runoff depth yearly. Area of all selected catchments are less than 170km2, acceptable hydrometric data time series long equal 6 to 27 years and so all of them located in and around of Zanjan province. At every selected catchments depth of precipitation, runoff and potential evapotranspiration (Blanney- Criddle method) estimated for every year. Based on gathered data and information, determined the calibration coefficient (only calibration variable parameter) of a mathematical model named (GR1A). The optimization criterion of calibration coefficient is the maximization of Nash-Sutcliffe coefficient as agency of model performance. Result is that the percent of Nash-Sutcliffe coefficient is 63.5 to 35.4 and acceptable at 4 catchments but is invalid at others. The invalid of Nash- Sutcliffe coefficient is affected by imprecise measured data, especially hydrometric data. So calibration coefficient of mentioned model is 0.11 to 0.24 at accepted catchments.

Soil structure and aggregate stability affect soil erodibility. There is a necessity for increasing aggregate stability against erosive factors such as wind and water. This study conducted on surface soil samples (0-20cm) collected from agricultural land susceptible to erosion located in the south of Fars Province. The experimental design was CRD with 10 treatments of control plot (without addition of soil amendments), pure gypsum, chopped wheat straw, animal manure, wheat straw and gypsum, animal manure and gypsum (1% w/w), cement (0.3, 0.6 and 0.9% w/w), and gypsum and cement (0.9% w/w) in 3 replicates. Amounts of soil aggregates in 53-4000 mm sizes were determined by wet sieving and MWD was calculated after one, four and seven months. After seven months, the results showed that the wheat straw, wheat straw and gypsum, and animal manure and gypsum treatments 2.7, 3.5 and 1.4 times respectively increased the MWD compared to the control. Generally, based on the results of this study, application of wheat straw with gypsum, wheat straw and animal manure with gypsum for increasing the stability of similar soils is recommended.

The aim of this study was the selection of appropriate depth and spacing of pipe drains in order to decrease installation costs of drainage network per unit area. A model was developed to estimate construction costs using soil and plant data for Behshahr region. The results showed construction costs decrease with increasing installation depth, as reduction in costs in shallower drain depths (<1.8 m) was higher, compared to greater drain depths (>1.8 m). When environmental effects are considered in addition to installation costs, the optimum range of drain depths are between 1.6 to 1.8m whereas the minimum costs would be related to the 2.8m depth. Furthermore over- and under-estimation design factors and transportation distance for envelope materials had considerable effect on construction costs, and this effect was more intense for shallower drain depths.

Drought is an important environment stress that influence on the growth of the flora. To determine the stability mechanisms to stress in four Agropyron species at test with four different levels of osmosic potentials resulted from PEG 6000 including 0, -3, -6 and -9 executed in factorial and accidental manner with four interactions in hydroponic environment. In this study the four species of Agropyron (Ag. intermedium, Ag. trichophorum, Ag. pertenus, Ag. podpera) and four drought treatment (-3, -6 and -9 times distilled water) water used. In this essay the sprouting percentage, root length, shoot length, seedling length, root length to shoot length rate, seedling dry weight, seedling fresh weight, dry to fresh weight rate sprouting rate and seed health index were determined. The results showed that with increasing the drought stress, the root shoot proportion, seedling weight and dry weight to fresh weight of Seedling factors increased and other attributes were reduced significantly. The best levels to assess the stability to drought were the -6 and -9 load potentials in all drought levels. In general, in tested species, Ag. trichophorum species showed a better sprouting in under study potentials and had a meaningful preference to other species. From assessed parameters, Seedling length and seed index standard showed the most possible reaction to changing potential of water.

In order to evaluate pollution of sedimentary environment, there are several different methods, among wich enrichment factor could be the most useful one. Therefore, in this research, the Anzali Wetland was divided into four different sections namely, Abkenar, Siakishom, Hendekhale and eastern section (Shijan) and then sediment corings were done for them. Afterward, concentration of main and subsidiary elements were determined using ICP-MS. Then the background levels of Cd, Cu, Pb, Zn were determined with different analytical methods. These methods were, use of concentration of elements in their lithology background, use of concentration in the collected sampled cores, normalization by Aluminum content, use of world mean concentration, use of EPA3050 standard and use concentration of elements in the soils of the wetland as background level. In the next step, the enrichment factors of Cd, Cu, Pb, Zn elements calculated by diving into the background level concentration. The results showed that enrichment factor which is used Aluminum as the normalization factor was the most suitable for sediments of this wetland. Therefore, use of this method is recommended for future heavy metal pollution study of this and the similar sedimentary systems of the Caspian Sea coastal zones.

plants in Rangelands intercept part of rainfall with out increased soil humidity. in this study was carrid out plant morphological characteristics (large and small diameter, canopy diameter, plant height, size and level of cover), physiographic factors (altitude, slope and percent slope) and rate of interception in Astragalus parrowianus. Average of plant size and volume were recorded, and considering the class using a rapid (Quick sort) of the base and the two groups were separated from each other. The first group bases with 0.002 to 0.02 m3 and second base with size 0.02 to 0.087m3. Data collected to assess the correlation and simple linear and multivariate regression models were introduced to Minitab statistical software. Results showed that the first group with an average level of cover 642 square centimeters, has 4.421 percent interception and in the second group with moderate precipitation and surface cover 1, 640 square centimeters, of interception 1.85 percent of the total precipitation. In the first group, grab the 1% level and significant negative correlation with the large diameter of the canopy (R=-0.729) and the 5% level with the canopy level (R=-0.507) is. In the second group, interception and significant negative correlation at 1% level of cover (R=-0.929) with small diameter canopy (R=-0.874) with large diameter canopy (R=-0.76) and plant size (R=-0.83) is shown. with increasing size and increasing the volume of voids in the canopy, the level of abstraction is reduced. Using regression models obtained from the estimated level of interception without stopping and re-weighing the plant is obtained.

In this study applicability of three landslide hazard zonation models including weighted density area bivariate statistical model (semi-quantitative model), multivariate stepwise regression model and logistic multivariate regression model (quantitative models) have been compared for the Chehel_Chai watershed in Golestan province to prepare risk map based on the hazard map of superior model. Landslide distribution map of the study area was prepared using air photos interoperation and field studies. Then nine parameters including elevation, slope, aspect, lithology, distances from fault, stream and road, land use, and annual precipitation were chosen as landslide effective factors. Potential landslide hazard maps were provided using three models. Chi-square test was used to analyze difference between hazard classes of models. Kappa index was used to compare the conformity rate of the hazard maps. Qs index was also used for evaluation of models accuracy. Hazard map, elements at risk map and vulnerability map were used in the preparation of risk map Results show that measured Chi-square statistics is statistically significant at 99% of confidence interval, and there is an appropriate differentiation among landslide hazard classes. Kappa index between hazard maps of models vary between 0 to 0.2, indicating that there is a slight conformity between them. Weighted bivariate statistical model has been identified as the superior model for Chehel_Chai watershed with Qs equal to 3.622. According to the risk map 7.67% of the study area is in high class and 5.37% of the area placed in very high Class.

The purpose of this study was to assess changes in pan evaporation over the period 1985-2005 in a network consisting of 14 synoptic stations of Iran using parametric and non-parametric methods. All seasonal and annual series have been checked for normality with the Kolmogorov-Smirnov test. Time trends of this variable were analyzed using parametric and non-parametric techniques (Pearson correlation coefficient, least square linear regression, Mann-Kendall and rho-Spearman correlation coefficient). The results showed that based on the Mann-Kendall test, 21.5% of annual series, 7% of Summer and Spring series had an increasing trend. Besides, 50% of Summer series, 43% of Spring series, 14% of autumn series and 21.5% of annual series showed a decreasing trend. Based on Pearson correlation coefficient, 28.5% of annual series, 7% of Summer and Spring series had an increasing trend. Similarly, in 21.5% of annual series, 43% of Spring series, 50% of Summer series and 14 % of annual series a decreasing trend was observed. The study indicated, 57% of summer series have significant series using Mann-Kendall, rho-Spearman correlation coefficient and Pearson correlation coefficient. In general, decreasing series were more than increasing ones. Despite of slightly increasing temperature trend previously reported in different regions of the country, results of this study showed that evaporation paradox does exist in different climates of Iran also. These reduced values of pan evaporation, as a key element in arid and semi arid climates of Iran, would have a significant effect in hydro-meteorological studies.

Some dry lands afforestation projects are accomplished in Rocky slopes. Rock crevices of rocky slopes provide suitable microsites for small tree. In this study we measured amount of EC, pH, organic materials, CaSO4, CaCO3, soil texture, N, P, K, soil moisture and gravel in soil on rock crevice of limestone lithology that three small tree establishment in these. The results show significant differences between soil moisture of 10-30 and 30-50 cm depth between crevices that different small tree establish, but our result doesn’t show significant differences on other soil characteristics between different small tree establishment sites, also these results show that there is only difference significant on soil moisture between live and dieback small trees establishment site. It was concluded that the amount of soil moisture could be played key important role in small tree survival and establishment on limestone rocky slope in arid lands.

Increasing demands for water and water shortage with low precipitation in Hamedan –Bahar plain have increased the rate of water consumption especially from ground water, during past 20 years, water table have decreased 0.84 meter, every years. In this research for evaluating management scenarios on condition of aquifer in future years, PMWIN model was used. Water fluctuations of 20 piezometric wells for two water years (2004-2006) were simulated. Model was calibrated in steady and unsteady states and then, the model was validated for one year (2007). Testing two scenarios on condition of aquifer during 5 years (2008-2013) that were, continuation of current utilization of ground water without increase of long term average precipitation and continuation of current utilization with 20% increase in average precipitation, shows that, if the current condition continued, as this way, more depletion of water table will occur in the future even with increase of precipitation. Other three proposed scenarios are: omit of unauthorized wells, changing cultivation pattern, and changing irrigation method. Evaluating the results of these scenarios shows positive influence on water fluctuation during future and cause decrease of water depletion. Among these, changing cultivation pattern have the most influence because of greatly volume of water that saving in this scenario.

Soil seed bank is an important part of plant communities. The study of soil seed bank could give us important information for rehabilitation of degraded vegetation. This study aimed to evaluate soil seed bank potential for recovering of degraded vegetation in Vaz watershed. In 2010, soil sampling was done along 4 transects within two different depths (0-5 and 5-10 cm). Relative frequencies for each species in both seed bank and aboveground vegetation were calculated. The relative frequencies in each plot were divided into landform and palatability classes for seed bank and aboveground vegetation. Paired t-test was used to compare density of soil seed bank between two depths, to compare each palatability class between seed bank and vegetation and to compare relative frequency of each landform between seed bank and vegetation. ANOVA and post hoc tests were used to compare palatability classes between soil seed bank and vegetation, separately. The results showed that soil seed bank density in upper depth were significantly higher than deeper depth. Relative frequency of III class was higher that I and II in both seed bank and vegetation cover. Land form for all levels was significantly different between seed bank and aboveground vegetation. We could not rely on the seed bank for increasing palatable production while soil seed bank could be used for soil reservation purposes.

The Gilan province has several rivers which the most of them are full of water and usually over flow in spring. Raining over the altitudes which covered snow, with high intensity showers result overflow of rivers and cause many damages like flooded passages, farms and residential areas in inferior and middle parts of catchments. Of course, the method of taking advantage of the area near river, as traditional way which is done in province, especially in inferior parts, cause various problems in the province of Gilan. So that human enforce make overflow of rivers and it's side effects in recent years. The inappropriate taking advantage of river recourses as irrelative utilized water, Tourism aspects, fishier activities, around the river and water diversion. These are examples of inappropriate management which damages rivers of province. On the other hand the ascending needs for water in order to agricultural activities and increasing tourism aspects in The Gilan province cause numerous that human enforces make to bed of river. So that irrelative harvest of sand from bed river, to empty trash, building garbage urban, rural sewage in the river and grazing more than the capacity of pastures and forest, and damaging the forest covering result ascending the discharge capacity of surface runoff and rivers and occurrence flood of rivers. One of the following events is criminal and financial damages and increased frequency of flood. While the environmental damages caused by floods and overflow of rivers are also significant and reaches to tens of billions. Therefore the results of the review and study in the range of 13796 km2 area. Province of Gilan consisted of the following 3 main catchments of Talesh, Anzali, Sefid-Rood and watershed in east of Gilan has been carried out, show that the damages caused by floods in the current studied watershed including death of 39 persons and loss amounts to 125.9 billion Rials in years of 1971 to 2001. So that these damages occur in 53 events flood at the sometime furthermore showers, floods, have been led to negative consequences in urban and rural environments and bio-economic level in farm and farm crops and infrastructure including communicational networks. Therefore, in order to solve this problem consideration to the management strategy in observation to substrate of river and decreasing the non principles that human enforce make, is necessity.