灌溉排水系统工程

This paper presents an internally coupled flow and solute transport model for free-draining irrigation furrows. Furrow hydraulics is simulated with a numerical zero-inertia model and solute transport is computed with a numerical cross-section averaged advection-dispersion model. A procedure for integrating the furrow volumetric cumulative intake integral in the context of a hydraulic model is presented. Two hydraulic and solute transport data sets collected in sloping free-draining test furrows were used in model evaluation. Soil intake and hydraulic parameters were estimated with a simple approach that matches simulated and measured flow depth hydrographs. The field-scale Weighted Mean Relative Residual (WMRR) between measured and model predicted flow depth hydrographs are 22.0% and 29.0% for the two data set. Furthermore, it is shown that the WMRR of 29.0% reduces to 16.0%, when only the error associated with the downstream end computational node is excluded. This suggests that a significant fraction of the error is related to the form of the downstream boundary condition used. It also shows that the effect of the downstream boundary condition does not extend to a large segment of the flow upstream. The longitudinal dispersion coefficient is approximated with an explicit equation as a function of the hydraulic and geometric variables. Model evaluation is conducted in three steps: (1) cumulative intakes and intake rates computed with the numerical formulation presented here were compared with a subsurface flow model, HYDRUS-2D; (2) solute breakthrough curves computed with the coupled flow and transport model were compared with those from exact analytical solutions for applicable conditions; and (3) model predicted solute breakthrough curves were compared with those obtained from field measurements. Overall the results suggest that the coupled flow and transport model is a useful irrigation and fertigation system management and evaluation tool.

This research conducted over the extreme rainfall intensity - duration - frequency (IDF) relationship, covering return periods from 2 to 100 years. Therefore, this paper presents an analysis of extreme rainfall data from Makoran region, for durations from 15 minutes up to 12 hours. The results are compared with analysis by others of data from other countries, which served to highlight an anomaly in the longer duration results. The shorter duration results are still considered plausible and potentially useful pending more detailed analysis of longer data sets. The statistical analysis of shorter duration rainfall data indicated considerable flood alleviation purposes to that particular study area. The results show the success of both short-term rainfall analysis models for forecast floods in real time. However, study aims to forecast monthly rainfall using time series models and determine appropriate observation data according to different districts rainfall conditions. The flood in Makoran showed conclusively that flood hazard in the area poses a large and yet, untamed problem for both the regulatory body (public) and the local authorities. With increased development in the floodplain the economic implications are likely to grow significantly therefore, a number of mentions the issues are paramount to the area of Makoran.

In the fixed rotational irrigation system of Pakistan, canal water supplies are usually deficient to meet crop water requirements. Therefore groundwater is widely used to supplement surface supplies. In most of the canal command areas, groundwater is used in conjunction with the surface water to decrease the salinity of irrigation water in an attempt to avoid soil salinization. However, conjunctive use of surface water and groundwater is equally practiced in head and tail ends of the canal system. This results in rising groundwater tables leading to waterlogging in the upstream areas and aggravating salinity problems in the tail areas due to less canal water availability and the poor quality of the groundwater. Therefore strategies need to be developed for surface and groundwater use in such a way that equity in availability of water of acceptable quality is ensured all along the channel. This paper suggests three options to achieve this objective; (1) development of guidelines for proper mixing ratios of surface water and groundwater to maintain acceptable salinity levels; (2) revisiting canal water allocations to provide more canal water to tail-end farmers due to poor quality of groundwater whereas encouraging head farmers to extract more groundwater to meet their demands; and (3) facilitating farmers to develop on-farm storage ponds to store their meager share of canal water and use it through high efficiency irrigation systems such as drip and sprinkler. All these options would require necessary changes in the government policies, institutional arrangements and wide scale dialogue with farmers. For this purpose, network of existing water user associations may play a vital role.

Modeling soil water evaporation and soil moisture are valuable for many applications in diverse disciplines. Ritchie and Snyder, presented different models to estimate soil water evaporation (ES) rate. The former also simulates the soil water dynamics at different soil depths. The objectives of this study were to evaluate the potential use of the S2000 model for soils with water content above θDUL in some parts of the profile and to evaluate R2009 ES model and compare its performance with that of S2000. The study was carried out at the University of Florida Indian River Research and Education Center in Fort Pierce, Florida in 2012 and 2013. Eight Time-Domain Transmissometry (TDT) probes were installed in a lysimeter filled with sand and measured hourly soil water content for six months. Three drying cycles (cases) were used for the evaluation of the models. R2009 underestimated the soil water content near the soil surface for Case 1 and 2. While for Case 3, R2009 estimated the near surface soil water content well for the first four days and then it tended to underestimate for the rest of the days. S2000 with the proper parameterization outperformed R2009 which overestimated ES. It was evident that getting the suitable parameterization for S2000 model was not always guaranteed. These finding may only apply for sandy soils similar to the one used in this study. Future studies should be done on different soils and diverse environment before generalization can be made.

Urban landscapes are the crucial key factors in natural human life stability in modern urban civilization. However, despite of the importance of urban landscape, common suitable urban landscape per capita in cities of Iran is between 7 to 12 square meters and the average urban landscape per capita in Urmia metropolis is 6.9 square meters, which indicates a serious gap for 20 to 25 square meters as global standards. On the other hand, the urban landscape growth for achieving global standards causes an increase in vegetation which by itself results in greater demand for water resources. Consideration of arid and semi-arid climate of Iran and limitation in water resources makes urgent need for planning and water allocation. The main purpose of the this study is putting forward a linear programming pattern in the form of transportation model in-order to allocate water optimally from the existing and future water resources (i.e., surface water, ground water and drinking water) to Urmia urban landscape pieces, considering minimization of the cost of supplying water. To achieve the above mentioned model, North-West Corner method, Least Cost method and Vogal Approximation method have been applied and the obtained results have been compared. According to the obtained results, in summary, it can be claimed that Vogal Approximation method, has the higher capacity for optimal allocation of water resources in Urmia urban landscape than that of Least Cost method as well as North-West Corner methods With regard to the present availability of water resources for every seven months of irrigation, the amount of optimal allocation of water from drinking water is 5400 cubic meters per day for boulevards, 1400 cubic meters per day for nurseries and 1200 cubic meters per day for other landscapes. The allocated optimal amount of water from surface water resources is 6500 cubic meters per day for forest parks. The allocated amount of ground water resources is 5000 cubic meters per day for parks in urban areas and 1600 cubic meters per day for boulevards and 900 cubic meters per day for forest parks. During the hottest month of each year (June 22nd to July 14th), with respect to irrigation, given the above variables in optimal allocation of water resources for urban landscape in the city of Urmia in comparison with that of seven month irrigation, are the same. However from quantity point of view, drinking water and ground water quantity, in some landscapes are less. Also, concerning the optimal allocation of water from future water resources (increment water supply), given variables such as mentioned above are present in the existing conditions. However, the quantity of groundwater usage for some landscapes is more. Finally, through the aforesaid allocation, only a portion of water demand for the pieces of Urmia landscapes has been partially met and the existing water resources would not be sufficient to bridge the gap.