Journal of Water Resources Engineering
Year:2009 | Volume:2 | Issue:4|Papers Count:8

Developing a rainfall-runoff model for an ungauged watershed provides the opportunity to estimate the peak flow, flood volume and flood hydrograph for that watershed. In this study, a rainfall-runoff model was developed for the Kasilian Watershed in the province of Mazandaran northern iran using the GIS system, the SCS method and the HEC-HMS hydrologic model. By using the HEC-GeoHMS extension and the digital elevation model (DEM) in the geographic information system domain (ARCVIEW software), the physiographic model, the sub-basin boundaries and stream networks for the Kasilian Watershed were defined. By incorporating the soil hydrologic group and land use maps, and the initial moisture content information in the GIS system, the curve number (CN) diagram of the Kasilian Watershed sub-basins was prepared. The SCS method was selected for simulating the flood hydrograph, and the Lag method was used for river routing. The watershed physiographic model was transferred from the GIS system to the HEC-HMS program, and the hydrologic model for the watershed was determined. By using several rainfall events and the observed flood hydrographs, the parameters of the watershed hydrological model, including initial loss and lag time of the sub-basins, were optimized. using to the mean optimized parameters, the model was evaluated for three different rainfall events. The developed model accurately predicted the values used in constracting the flood hydrographs for 2 events. However, that for the 3nd event had an error range of 10-15%, which were within the acceptable range.          

Spatail variability of rainfall has diverse effects on the management and planning of water resources on a watershed, as well as on the national scale. Spatial variability analysis of different parameters, e.g. rainfall, can be very important in estimating the water balance uncertainties and in the decision-making processes. In the presence of Spatail correlation between observations, application of Geostatistical interpolation methods provides usually provides close estimation of the sought values. This technique was implemented in the deformination of the abundance of the 24 hr maximum rainfall of 27 rain guaging stations in Golestan plain.The methods used were ordinary kriging, cokriging and weighted moving average. Cross validation was used to evaluate different interpolation methods. Statistical analysis showed that winter rainfall had the smallest coefficient of variation in comparison with the other time periods used. Geostatistical analysis showed a strong spatial correlation of the data; the best semivariogram model was spherical. The cross-validation results indicated that except for winter, cokriging results in a smaller error for rainfall estimation. Moreover, the generated rainfall maps indicate that the northern region of the presence reccives leave amount of precipitation.

Evapotranspiration (ET) is the largest water consumer in arid and semi- arid regions. Therefore, acquiring the knowledge of the factors and processes leading to ET is of utmost importance in decision – making water resources management. In this study, the long time trend in mean monthly temperature, rainfall and ET was investigated to this end, all synoptic stations were categorized according to the De Martonne climate classification method. As we were mostly concerned with the semi- arid region of the Land of Iran, only 14 stations with at least 30 years of data were selected for this purpose. The least squares error, the Man – Kendall, and the Vald-Volfoyts methods were used in analyzing the data. The FAO-Penman-Monteith equation was used in the reference crop ET estimation. It was observed that 24% of the stations showed positive and 14% showed negative trends, and the remaining stations did not follow any trend. As for the rainfall, no meaningful trend was detected in this parameter. Of the applied statistical methods, the least squares and error the Mann-Kendall methods showed closer similarities than the other procedures. In conclusion, it is certain that some regions shall experience higher temperatures, thus ET, in the coming years.

Precipitation data were collected from 33 synoptic and rain gauge station of the Fars province for the 1971-2008 period. The standard Precipitation index (SPI) was used to identify the short (1, 3, 6 mounths) and long (12, 24, 48 mounths) time drought periods. The geographic information system (GIS) was used in delineating the drought crisis threshold (DCT) for different regions of the province. It was observed that moderate intensity droughts rank most in the province ranging 17–46% Droughts lasting one year was the most prolific, and those lasting 4-5 years had the least abundance. The DCT for the winter precipitation ranged 267-478 mm for the higher rainfall regions, and 56-162 mm for the lower rainfall regions. Generally, the southern, easthern, and part of the wester and central regions of the province experience more droughty periods than the rest of the province.

Management of the density jumps in lakes and reservoirs plays an important role in the water quality improvement and in the sediment deposition and erosion management. The density jump was studied experimentally by considering the bed roughness. Experiments were performed in a rectangular laboratory flume having a gravel bed. Using the collected data, a simple relationship was obtained for estimating the conjugate depth ratio in relatively weak jumps. The conjugate depth ratio is independent of the entrainment ratio, and depends only in this relation on the upstream densimetric Froude number and the relative roughness. For smooth beds, the spatial development of the density current was also analyzed in both supercritical and subcritical flow regimes. As the distance from the end of the jump increased, the maximum velocity drifted towards the bed. Finally, at a distance approximately fold h2 from the end of the jump, the non-dimensional vertical distribution of mean velocity had a shape similar to that of the supercritical section.

The main objective of hydrological studies is to provide water of good quality with strict specifications for drinking, agriculture and industry.Corrosion and scaling are some of the problems affecting the distribution systems. To assess the scaling and corrosion potential of the Bahar Plains groundwater, the Langlier, Raisener and Puchorius criteria were employed of the two deleterious properties of groundwater in the Plain, scaling occupies the first ranking. While scaling takes the second ranking. As for the scaling, qanatwater is of better quality than wellwater; a reason maybe the shortening of the galleries through shortcut tunneling. It was observed that 95.7% of wellwater have the scaling potential according to the Raisner criterium; however, this decreases to 53.2% if the puchorius index of 6 is taken as the upper limit of scaling. Employing the Piper curve as the standard, the following conclusions are reached: 70% of the sample contain calcium bicarbonate, 14% contain sedic bicarbonates 4% contain calcium sulfate, 5% contain magnesium bicarbonate, 4% contain sedic sulfate, and 3% contain calcite chlorite. These results also indicated that the langlier criterium is not suitable for assessing the scaling and corrosion potential of the groundwater. In conduction, Bahar Plain groundwater has a low to medium potential of scaling and potential; however, its scaling potential is higher than that of the corrosion potential. This decreases the cross sectional area in the water distribution system resulting in the head loss.

Minab Esteghlal Dam which is located in kilometers 4, east of Minab town, was operated in 1362. The proposed functions of the dam were supplying domestic water to the cities of Minab and Bandar Abbas, irrigation water to the command area, water for industrial complexes, the artificial recharge of groundwater, and flood mitigation.This study was implemented to assess Physico- chemical impact of the dam on the regional environment. In addition to the field survey, water sample were collected at the entrance of the Minab River to the reservoir and at the water treatment plant. The samples were analyzed for TDS, COD, EC, BOD5, DO, SAR, pH and the sum of anions and cations. The AHP was utilized to assess the effects of different factors that deeply affect the environment. As the watershed, particularly the mountains surrounding the reservoir, mainly consist of highly erodible calcareous-marls, thus causing accelerated sedimentation of the reservoir and turbidity of the water, geology physiography attained the first (0.324) and 2nd (0.147) ranking. Annual rainfall and its shortage (102.9 mm mean annual rainfall during the 1999-2004 periods) attained the 3nd ranking (0.068). The detailed ranking of other factors are described in the article. A few vital guidelines for the operation and maintenance the reservoir are presented in the conclusion section.

The available discharge and electrical conductivity (EC) data of 46 hydrometry stations on the Bakhtegan Basin were collected and their correlation were determined using the Pearson and Kendal methods.The results showed that both methods followed similar trends in most stations. Model selection was based on the achieved higher correlation coefficient; for those stations that correlation coefficients were close, but there were outlier data the Kendall method was suggested. Finally, there was a strong, negative correlation between the discharge and EC, for which the regression equations were developed, and all of the relationships were statistically meaningful. These station were: Shorekharestan-Jamalbig station on the Kor River, and Sivand-Polekhan, Sivand-Dashtbal, Sivand-Emadabad and Cheshmebeno-Mashhademorghab stations on the Sivand River.