IRAN-WATER RESOURCES RESEARCH
Year:2006 | Volume:2 | Issue:1 (4)|Papers Count:11

Transport and contaminant discharge Simulation from coastal aquifers into seaward is complex due .to boundary condition in seaward. In this research, ModSharp, a numerical model has been developed that is able to simulate contaminants transport in large scale in coastal aquifers. This model solves Advection- Dispersion equation with method of characteristics. The accuracy of the model was evaluated for several idealized problems for which analytical and numerical solution, in field of seawater intrusion and  contaminant transport could be obtained. Effect of seawater intrusion on contaminants transport in coastal aquifers as simulated. Simulation results show that seawater intrusion has significant effect on solute transport in coastal aquifers. Neglecting the influence of seawater intrusion leads to a lower estimate for rate of contaminant discharge to sea.

Serious damages have been reported in hydraulic structures due to cavitation. It is known that introducing air into the flow will considerably reduce cavitation risks. Thus, aerators are used in many situations to introduce air into the flow and to eliminate cavitation tendency. Although many works have been reported for flow aeration in outlet conduits of rectangular sections, less information can be found for circular tunnels. These structures are commonly used to supply water for hydroelectric power plants or drinking and irrigation systems. In this paper, experimental information regarding the intensity of pressure fluctuations and its dominant frequency downstream of rectangular aerators in such structures are provided. Experiments were performed in a circular pipe of 28.8 cm diameter. Rectangular aerators of different heights and angles were fixed inside the tunnel and air was supplied through aerator to check its effect on the intensity of hydrodynamic pressures. This information is useful for the structural design of such outlet tunnels.

One of the major governing factors in flood trends is the changes in land use. Golestan Dam basin in North- East of Iran has recently experienced devastating floods. Land use changes are believed to be partially reponsible for this flood intensification. In this paper, using GIS tools and HEC-HMS model, the effects of changing vegetation cover on flood hydrographs in Golestan Dam basin are assessed. The flood condition corresponding to two limiting land use scenarios are then evaluated. Landuse maps from 1967 and 1996 along with the soil map were overlaid using GIS tools to produce CN maps. HEC-HMS hydroloigc model was calibrated and validated based on three methods; curve number (CN) method for infiltration, SCS unit hydrograph for subwatershed rainfall-runoff routing, and Muskingum method for river routing. The results show that recent changes in land use has caused upward trend in flood magnitudes of different frequencies, e.g., 31.7 and 17.8 percent increase in flood peak corresponding to 5-yr and l000-yr return periods, respectively. This impact reduces as return period increases. Also, the results of deteriorating land use in the pessimistic scenarios show that loss of forests and rangelands increases flood peaks of 5 and l000-yr by as much as 35 and 24 percent, respectively.

Using continuous classification (specifically zonation in this study) it is possible to save continuity of changes in natural phenomena while representing them. Fuzzy Sets Theory is a proper tool to study and represent this continuity. As a case study in application of Continuous Zonation, fuzzy clustering among many other pattern recognition methods was applied to study erodability of Tajan river watershed. The results have been compared with traditional PSIAC method and have been represented as continuous erodability maps by using pixels value combination method. The maps show that even in area that a class is dominant, changes in erodability are visible. Also classes, which do not really exist and are only the artifacts of crisp boundary. classification, are omitted. Transitional changes can be modeled similar to real gradual ones in nature.

This paper shows concurrent application of The Artificial Neural Network (ANN) model with Fourier Series ARIMA Model (FSAM).The FSAM model represent spectral analysis of precipitation of Barandooz river basin in west of Lake Urmia for simulation of river flow. Neural network are applied for simulation and forecasting of Barandooz river based on FSAM forecasts in the absence of precipitation data. Because temperature is one of the independent variables in the simulation model, generation of temperature data was carried out by twelve MLP Neural networks, one for each month. The analysis and results are presented in this paper.

In 1961 Hershfield introduced a statistical method to estimate probable maximum precipitation (PMP). His method was based on the data of maximum daily precipitation of 2645 stations. Occurrences of rainfalls greater than PMP in the upcomming years, questioned Hershfield's method. Eliason (1997) presented a multi-station method. Since PMP can occur at every point within a homogen region, this method was based on a combination of data from all stations in such a region. Gumb1etype 1 and its derived distributions were used as a mathematical tool. For parameter estimation however, Eliason used method of moment. In this paper, three other methods are used, namely maximum likelihood, maximum entropy, and probability weighted moments. Data of 41 homogen stations from North of Khorasan Province in Iran was utilized for comparison purposes. The performance of maximum likelihood was proved via statistical analysis. In addition, PMP is compared for all stations using modified Hershfield method. Results were compared with multi-station method and showed the performances of the former.

Prediction of annual precipitation usually guarantees success in dry-farming and promises a better pasture management. In this research, the long-term observed daily precipitation for 28 different stations in Kerman province was analyzed. Starting from the first day of autumn, a good linear relationship is obtained between the days with 47.5 mm precipitation (t47.5, day), and the amount of annual precipitation (pma, mm). Furthermore, to increase the correlation coefficient of this relationship, long-term mean annual precipitation (Pma, mm), elevation, longitude, and latitude for each station were also used in the multiple regression analysis. The results showed that none of these factors (i.e., elevation, longitude and latitude) could improve the correlation coefficient. The independent variables were Pma and t47. As another independent variable, temperature of the water in Persian-Gulf (south of region) in the water-air frontage were added. The three-month cumulative surface temperatures in autumn (Tau, ˚C), improved the correlation coefficient of the multiple regression. These final equations were used to predict the annual rainfall in Baft-soltance station. The results showed that the both simple models could predict wet and dry years sufficiently well but the error of estimation in the second model was lower.

The complicated structure of the surf zone with a strong unsteadiness has prevented us to fully understand its internal structure. Numerical models are one of the best tools to study hydrodynamic phenomena in this zone. In this paper, a two-dimensional vertical (2DV) model is proposed to study breaking waves in front of seawalls. The numerical model consists of an unsteady hydrodynamic module in which the fully Navier-Stokes equations in vertical plain are solved using the projection method. Finite volume method is employed to discrete convection and diffusion terms of governing equations with Froum and Crank Nicolson methods, respectively. The free surface water is tracked by using the Young technique. Using standard k - f. model to simulate turbulence effects showed reasonable results. Finally, the numerical results are compared with wave flume measurements for the same conditions. The result of the proposed model shows close agreement with experimental measurements in terms of surface elevations, horizontal and vertical velocity and flow pattern in front of the seawall.

The Zayandeh-Rud Basin (ZRB) is experiencing water stress. It has been the situation for the past 50 years. Basin development is considered normally a three-stage process with a relatively smooth transition between overdraft, water supply management, and optimal allocation. In the ZRB however, five phases of water resources developments (WRD) may be identified, including the trans-basin projects. The Situation in the ZRB does not show an encouraging picture. Increased water supply on each phase of development still fall behind the demand growth. That is the reason why for the past 50 years, the basin remained more or less under water stress. There is no inter-basin integrated water management that shares out the shortages uniformly between different uses, or even within a particular water use. Without trans-basin water transfers, the ZRB basin is unable to meet existing water demands. However, several scenarios also show that even then, the basin will be unable to meet water demands before 2020 as long as the urban, industrial and agriculture sectors continue to grow with the current rate.