ECOPERSIA
Volume:3 Issue: 3, Summer 2015

Among different models for runoff estimation in watershed management, the Soil Conservation Services-Curve Number (SCS-CN) method along with its modifications have been widely applied to ungauged watersheds because of quickly and more accurate estimation of surface runoff. This approach has been widely accepted by hydrologists, water resources planners, foresters, and engineers, as well. Therefore, this work was aimed to estimate the curve number using CN-values through several methods viz. SCS, Sobhani (1975), Hawkins et al. (1985), Chow et al. (1988), Neitsch et al. (2002) and Mishra et al. (2008) in Bar Watershed, Iran. According to the results, the Neitsch formula showed the best performance for estimating the Curve Number in situation with low (CNI) and high (CNIII) antecedent moisture conditions. However, the weakest performance was related to Mishra (2008) in CNI and CNIII-conversions. The weakest performance was resulted from the exponential form of the Neitsch et al. formula and the variable meteorological conditions of the Bar Watershed over the year.

In the last decade, frequency of late cold incidence has increased in the upland forest nurseries. The aim of present study was to reduce the damage caused by spring frost and to increase the efficiency of Persian maple seedlings production in mountain nurseries. This study was conducted as split plot design with two main treatments and three replications in two consecutive years (2009-2010) in Farim Wood Company nursery, Mazandaran Province, Iran. Maple seeds were collected from a site located near the nursery. The main treatment was seedlings protection in two levels of covering the seedlings during the cold days and without covering. Sowing date was sub-treated and applied at six levels (2nd week of Dec., mid-Jan., 1st week of Feb., 3rd week of Feb., 3rd week of Mar. and mid-April).The results showed that seedling covered and seed sowing dates had significant (p<0.01) effect on reducing frost damage. Besides, interaction effect of sowing date and seedling cover was significant (p<0.01) in both years. There was no significant (p>0.05) effect between the sowing dates in protected plots. Overall, mortality of seedlings gradually reduced with shifting sowing date to March in uncovered plots. The maximum mortality rate was related to the sowing in 3rd week of February. Losses of seedlings were the same in covered and uncovered plots in mid-April sowing dates. In the unprotected plots, the maximum losses of seedlings were recorded in the sowing dates before March. In fact, if seed sowing of A. velutinum was postponed until early spring, the seedlings mortality rates were not significantly different in both treatments.

Constructionof underground dams is a practical solution to save groundwater in alluvium watersheds, particularly in arid and semi-arid regions where surface water scarcity is an environmental challenge. Considering socio-economic and environmental benefits of underground dams, the accurate locating is the primary consideration for dam construction. The new technologies and methods are a step toward the proper locating to reduce the risk of underground dam construction. In this study, two methods,decision making and geographic information system (GIS) were used for locating suitable places for underground dam construction in Hamedan-Bahar watershed where water shortage has been a serious problem during the last decade. In the first step, the effective factors in locating and construction of the dams underground were identified, and then their GIS information layers were created. The primary selection maps of suitable sites were provided using Boolean logic method in ArcGIS software. The Analytical Hierarchy Process (AHP) was then applied in EXPERT CHOISE. In the next step, the results of Boolean logic and AHP methods were overlapped to provide the final selection map. A consistency rate of 0.06, showed a relatively high accuracy of weighting process. Considering the normal weights, geology and distance of well, springs and qantas were found to be the most and the least effective criteria, respectively. Furthermore, the final selection map suggested the surrounding area and the outlet of the plain as the most suitable sites for dam construction.

Germination is a critical stage in the life cycle of plants and often controls population dynamics, with major practical implications. Salsola arbusculiformis is one of the most important plants used to prevent soil erosion and a good fodder resource for sheep and goat in the rangelands of Iran. However, the species seems to have low seed germination, so the purpose of this study was to investigate the effects of different treatments to improve its seed germination. Three concentrations of gibberellic acid (100, 500 and 1000 ppm), mechanical scarification with sandpaper, concentrated sulphuric acid (H2SO4 (98%)), potassium nitrate (KNO3 (0.2%)), thiourea one Molar, four prechilling periods (10, 20, 30 and 150 days at 2 °C) were used as study treatments and distilled water as control. The results showed that there were significant differences (p<0.05) among and within the treatments in their effects on seed germination. The effective treatments to stimulate seed germination were prechilling for 150 and 30 days; sulphuric acid and sandpaper scarification. Prechilling for 150 and 30 days increased germination by 88.4% and 85.65%, respectively, while sulphuric acid and sandpaper scarification both increased germination by 76.1% compared to the control. The results also showed that gibberellic acid, potassium nitrate and thiourea did not promote seed germination. It was inferred that the most effective treatments among the methods used for breaking seed dormancy of Salsola arbusculiformis were prechilling for 150 days and mechanical scarification by hand with sandpaper.

Flood water contains high amount of sediment affecting the fertility of the coarse grain alluvial fans and flood plains through increasing nutrients. In this study, the effects of the flood water spreading on the soil nutrients recovery were investigated during 10 years (2004-2014) at the Poldasht Flood Spreading Station of West Azarbaijan in Iran. Flooded three upper strips were selected at the flood spreading system. Three composite samples resulted from mixing four samples, in each strip were taken from 0-30 cm depth. Soil organic carbon (SOC) and total nitrogen (TN), exchangeable phosphorus (P) and potassium (K) were determined at the laboratory. To statistically analyze the data, t-test, in case of normal distribution, and otherwise non-parametric test of Kruskal Wallis were used. Results showed that the amount of SOC and TN increased from 0.23 to 0.33% and 0.027 to 0.039%, respectively. Noticeably, SOC, TN and P contents in the upper strips were significantly more than in the lower bands (p≤ 0.05). In addition, exchangeable P and K were significantly increased (p≤0.05) from 2.69 to 5.32 and 145.93 to 206.52 ppm, respectively, but there was no significant change in (p≤0.05) K content. These results also showed that flood water spreading increased the soil nutrients which may reduce the fertilizer requirement.

The present research was planned to evaluate the skill of linear stochastic models known as ARIMA and multiplicative Seasonal Autoregressive Integrated Moving Average (SARIMA) model in the quantitative forecasting of the Standard Runoff Index (SRI) in Karkheh Basin. To this end, SRI was computed in monthly and seasonal time scales in 10 hydrometric stations in 1974-75 to 2012-13 period of time and then the modeling of SRI time series was done to forecast the one to six months of lead-time and up to two seasons of lead-time. The SRI values related to 1974-75 to 1999-2000 were used to develop the model and the residual data (2000-2001 to 2012-13) were used in model validation. In the validation stage, the observed and the predicted values of SRI were compared using correlation coefficient, error criteria and statistical tests. Finally, models skills were determined in view point of forecasting of lead-time and the time scale of drought evaluation. Results showed that the model accuracy in forecasting two months and one season of lead-time was high. In terms of the forecasting of SRI values, the skill of SARIMA in monthly time scale (with a RMSE and a MAE of 0.61 and 0.45 respectively and a correlation coefficient average of 0.72) was better than its skill in seasonal time scale. The application of SARIMA in monthly time scale was therefore preferred to its application in seasonal time scale.

The main diatomic structure-forming species of the Zayandehrud Reservoir was investigated by collecting samples from the surface, five, seven and 10 m depths from January 2011 to October 2012 along four linear transects. Asterionella formosa Hassall, Cyclotella ocellata Pantocsek and Fragilaria crotonensis Kitton were revealed as the three structure-forming species among diatomic algae in the reservoir. The number of these diatomic cells increased from the reservoir banks to its central areas, but their abundance was non-uniformly distributed at the 10-meter water column at different sites, except for C. ocellata that showed a practically uniform distribution at the peak of its maximum growth. Overall, the frequency and cover of these structure-forming diatoms changed under the influence of different abiotic variables such as electrical conductivity (EC) and nitrate (NO3-N).