Watershed Management Research
Year:2011 | Volume:24 | Issue:2 (91)|Papers Count:12

Estimation of design flood is the first step in hydraulic structures and flood control projects designing. On the other hand, estimation of runoff and flood, need to precipitation and design rainfall informations.Therefore, with respect to the spatially variations of rainfall and providing Depth-Area-Duration relationship, we can obtain suitable patterns of rainfall for estimation of design rainfall values in various locations. In this study, after gathering all storms in Hamedan, Qazvin and Zanjan provinces, 9 maximun and overall storms from 50 storms were selected.The results showed that between all of storms, the November 5, 1994 storm is maximum and overall than others.The number of stations varies from 116 - 125 of 169 total stations in different storms. After drawing rainfall accumulation curves for climatology raingage stations, the hytograph curves were drived for noun recorded stations. After that the rainfall maps provided for 9 storms. Finally Depth-Area-Duration curves provided using rainfall maps. Using this curves were derived rainfall amount in any region and duration.

Importance of flood spreading related to soil resources is due to sedimentation of suspended materials in eroded lands. These lands are converted to fertile lands with high capability for developed agriculture. Entrance of flood with variable resources produces variability in soil properties. Therefore, trend of changes in total nitrogen (N), phosphorous (P) and potassium (K) were investigated in this research. For those purposes, the experimental stations were selected, based on soil properties, watershed characteristics and conditions of flood spreading sites. After selection of bands, sampling was done by the systematic-randomized method. Non-parametric test (Kruskal & Wallis) was used for statistical analysis because of data non-uniformity of (based on Kolmogorov-Simernov test). Variability of total N in stations of group I and group II increased in the final year in comparison with that of the first year. So, total N from the first to the third bands ranged from 0.03, 0.03 and 0.02 percentage in the first year to 0.04, 0.03 and 0.03 percentage, respectively in the final year. Also, P variability in stations of group I and group II increased from the first year to the final year. So, available P in the three bands ranged from 3.1, 5.03 and 3.99 mg/kg in the first year to 7.93, 9.09 and 5.89 mg/kg in the final year. In the stations of group II, available P in the three depths ranged from 7.35, 5.17 and 2.01 mg/kg in the first year to 9.25, 6.85 and 6.14 mg/kg in the final year. In the stations of group III, available P in the three depths ranged from 4.23, 3.1 and 4.74 mg/kg in the first year to 9.34, 6.95 and 6.72 mg/kg in the final year. In group I, available K decreased from the first year to the final year. So, available K from the first to the third bands ranged from 127, 133 and 128mg/kg in the first year to 111, 118 and 113 mg/kg in the final year. Despite the low quality of soil fertility prior to the construction of these stations, in general, floodwater spreading has considerably improved soil fertility.However, desirable objectives may be achieved in long term through occurrence of diverse flood events and suitable maintenance of the stations.

According to world meteorological organization study, winds with more than 15m/s (30knot) are identified as storm. Therefore based on this threshold in this study, the temporal and spatial distribution of storms in Iran has been analyzed and zoning. In order to achieve the purpose of this study, after gathering the data of wind direction and speed in stations of the country, a common 40-year period among 33 stations was extracted, then regime of wind speed, storms frequency and direction were calculated with help of SPSS and EXCEL software. Then, the data was entered in Arc GIS software then, temporal and spatial distribution map of storms in Iran was obtained and analyzed. The results of this study show that, March had the most average stormy days with 12 days, in Zabol station, August had the most average stormy days with 26 days. The most frequency of storms occurrence was at 12 with 609 frequency. In zabol station most frequency storm was at 06 with 841 frequency. Also, storm zoning shows that storms distribution in the country did not have fixed trend. In sum, Zabol station significantly had most frequency of storm occurrence. Zahedan, Kerman, Tabriz, Esfahan, Hamedan and Bandar anzali stations had high frequency occurrence.whereas, Khoram abad, Mashhad, Arak, Oromieh, Gorgan, Shahrud, Shiraz, Torbate heidarieh and Semnsn stations had the lowest frequency occurrence. The rest had the average storms occurrence. Also mean wind speed show that, in the more stations did not have significant relation between mean wind speed and frequency of storms occurrence.

Phosphorus (P) is an important nutrient for plants, in other hand P contaminates water resources. The present study aimed to access the applicability of rainfall and runoff variables of seven storm events occurred during 2008 in prediction of storm-wise peak and average P concentration and total P loss in Kojour watershed with the help of bivariate and multivariate regression models. Towards this attempt, seven storm events occurred during study period were analyzed, samples of river were collected for seven events with time intervals of 1 h. The results verified the capability of regression model with relatively high determination and efficiency coefficients of 0.884, 0.883 respectively. The results could facilitate the application of given methods obtained in the present study to other areas with similar conditions and leading to the suitable soil and water management.

Selecting the suitable shape and area of plot is very effective in sampling efficiency in vegetation studies and causes the least variance and time of sampling. to this purpose, for reduction of sampling time and increase of work speed comparing the plot size in estimating the quantitative characteristics of species (containing canopy cover percentage and density of species) in either enclosure and non enclosure area. For do this research, first established 1m2 plots and daubenmire (25×60 cm) plots randomly in the case study in two enclosure and non enclosure area and registered canopy cover percentage and density of species in each plot. Analysed and compared statistically data get of the plots with different size in inside and outside of enclosure. results get showed that vegetation type, plants distribution and measuring variable type have intensive effect on plot size and shape, according as optimum plot size differ for estimating the quantitative characteristics of species in two enclosure and non enclosure area. Therefore seem it is better using 1m2 plots and daubenmire plots for estimating the canopy cover and density in non enclosure and enclosure area respectively.

Soil response to pressures imposed by wheel and soil engaging tools is one of the most important factors, which can cause soil compaction. This research was to investigate the effect of inflation pressure on soil compaction related factors such as rut width, rut depth, cone index and horizomtal force in different soil layers profile using a flexible carcass tyre and a soil compaction profile sensor in controlled soil bin laboratory conditions. Studies were conducted at two level of inflation pressures of 90 and 227 kPa at three replications in a randomized complete block design. F test were applied to compare the means of pressure. Variance analysis of experimental data showed that there was significant difference between the mean values of soil cone index and horizontal force at depths of 10 to 40 cm of soil. While the mean values of those parameters was not significantly different at depths of 0 to 10 cm. However, the mean of rut width and rut depth at the two inflation pressures was significantly different. Increased inflation pressure decreased values of rut width from 75 mm to 70 mm and increased values of rut depth from 41 mm to 56 mm. The amounts of cone index increased from 4% to 21% and horizontal force increased from 9% to 37% at different soil layers by increasing inflation pressure. Results also indicated that soil compaction profile sensor can be used as a research and a practical tool under field conditions to determine the effect of inflation pressure on soil compaction.

The object of this research was to compare the amount of N, P, K, C and C/N in litter of three range species including Bromus tomentellus, Agropyron tauri and Psatyrostachys fragilis in order to determine the influences of these elements on soil quality indexes. Soil and litter sampling was done at the end of growing season (summer 2009) after identification the sites of these species in Taleghan. Sampling were conducted in the key area of each site based on random-systemic method. The samples were collected and transferred to laboratory, the amount of C, N, K, P, C/N ratio in litter and pH, EC, Lime and texture in soil were determined. After investigation of data, their analyses were performed by T.test analysis, analysis of variance and Duncan. The result of variance analysis showed that there was significant deference between of C, N and C/N ratio in litter of these species. The maximum of N was related to A.tauri and the maximum of C and C/N ratio was related to B. tomentellus. Comparison of under plant soil and control area showed that there was significant deference between under plant soil and control area and above species was increased soil fertility. In generality A.tauri was better than two other species in litter quality, speed of degrade ability and its effect on soil conditions.

Investigation of occurrence probability of drought characteristics (severity and duration) is considered as a stochastic analysis for drought zoning. This study combined these two features on 34 stations in central Iran for drought zoning. Firstly L-moment method was used to regional frequency analysis of drought severity and its duration. The results showed that although the study area based on drought severity is not homogenous, it’s considered as a homogenous region according to drought duration. Then Pearson III distribution function was selected as the best regional function for both characteristics. Results also proved that drought severity in the lower return period is almost uniform in central Iran, but in high return period, this parameter in eastern and southwestern of central Iran is higher than other regions. Also West regions, especially in Isfahan region due to longer severe droughts need to a crisis management and water resources management in order to reduce the destructive effects of this natural event.

Many studies have been carried out to assess and prepare desertification map in the world. In order to develop a regional model and quantitatively assess the present situation of desertification, a study was carried out in an area of 88350 hectares in Zahak region of Sistan. In this study, at first by combining information extracted from topographic and geologic maps, air photos and field survey, the area was divided into 11 geomorphologic facies; each of which was considered as the main unit for evaluation of the present situation of desertification. Considering to FAO-UNEP and MICD models are the most famous models of desertification intensity assessment in Iran and world. In this study, based on land use, effective indices emphasizing water erosion criterion were identified using to FAO-UNEP and MICD models. Then, the most effective of indexes was selected and a desertification area model was allocated. Also, the numerical value of indices was analyzed in each work unit and after all area. Finally, the present situation of desertification intensity of the study area emphasize of water erosion criterion in four classes of insignificant and low, medium, intense and very intense was estimated. The results indicate that in the developed regional model, the study area with respect to intensity of desertification is placed in about 4915 hectare (5.9%) in the low class and about 78599 hectare (94.1%) in the medium class. also the weight medium of quantities valuation estimated in the total area DS=15.19.That, it indicated the intensity of desertification medium class in the total area.

Salinity is one of the most important environmental factors that have negative effects on the germination, establishment and growth of plants and decrease the production of plants. To evaluate the effect of salinity on germination and seedling growth of echium, two separate experiments were conducted and the effects of different levels of salinity of natural and artificially made saline water (solution of NaCl+CaCl2) were examined on the germination of this plant. The experiments were carried out based on a completely randomized design with four replications. Treatments of this experiment consisted of different levels of salinity including (0, -3, -6, -9 and -12 bar), which were, respectively. The results showed that different levels of salinity in two types of saline water had a significant effect on the components of germination (P£0.01) and with increasing salinity levels, the amount and rate of germination and seedling growth (length and dry weight of radical and peduncle) declined. Of course, these traits decreased in natural saline water treatments far more than artificial saline water. Although echium seeds had 20% germination in salinity level -12 bar of NaCl+CaCl2 solution in natural saline water treatments, germination was negligible in salinity level-9 bar and completely stopped in salinity level -12 bar. Overall, the study showed that (1) echium plant seeds have germination ability in the salt environments, (2) germination rate depends on the type of salt composition in the growth environment, and (3) the inhibitory effect of natural saline water was far more than the NaCl+CaCl2 solution.

Soil salinity and sodicity are escalating problems worldwide, especially in arid and semi-arid regions. This study investigates the effect of some mineral and organic amendments on reclaiming a saline- sodic soil based on distribution of soluble cations. The soil amendments consist of control, cattle manure, pistachio residue, gypsum, manure + gypsum and pistachio residue + gypsum; water treatments with and without sulfuric acid with three replicates were performed. At the end of experiments soluble cations were measured at different depths. The results indicated that monovalent cations and also the EC and SAR showed the lowest values near the soil surface, while bivalent cations had no significant variation with depth. This finding shows that monovalent cations would be more mobile than the bivalents. Also, it was found that in comparison with gypsum, sulfuric acid had more efficiency in the SAR decreasing. However, in calcareous soils, this aim would be achieved by only irrigation. Pistachio residue and cattle manure had the highest and the lost efficiencies in decreasing of the EC and SAR. The findings of this research reveal the relative importance and efficiency of pistachio residue in reclaiming of the sodium affected soil.

In this research, desertification intensity of sistan plain was evaluated using IMDPA the newest method of Assessment of Desertification Potential in arid and semi arid regions of Iran. For this purpose 4 criteria selected including vegetation cover, soil, climate and wind erosion. Each criterion was assessed based on the selected indices which result in qualitative mapping of each criterion cased on geometric average of the indices. Then, sensitive map of region was extracted using geometric average of all criteria. Thematic databases, with a 1:50000 scale resolution, were integrated and elaborated in a GIS based on arc/info8, arc view3.2 and especially ILWIS. By laminate of thematic databases layers and using this formula DM=(SI×WEI× VI×CLI)1/4 to Calculate the geometric mean Criteria. Then Desertification intensity map was obtained with analysis IMDPA Model. The result showed that 51.09% of study area was found to be in medium and about 45.09% in high class of desertification. And while 3.82% of the region in clouding Residential and Water tanks (CHAH NIME) there aren’t in any classification. Analysis of desertification criteria in Sistan region showed that among study criteria, wind erosion criteria is a major problem with a geometric average of 1.67 which shows high class while soil with a weighted average of 1.34 has lowest effect in desertification. Also vegetation cover and climate criteria with a geometric average of 1.51 and 1.57 show middle class desertification.