Journal of Irrigation and Drainage Engineering

The important evaluation parameter in trickle irrigation is emission uniformity. There are two different methods to calculate emission uniformity; (1) field evaluation for the subunit and (2) using theoretical formulas to calculate emission uniformity during the design period. Emission uniformity is usually divided into two parts, namely, manufacturing, ${\mathrm{EU}}_m$, and hydraulics emission uniformity, ${\mathrm{EU}}_h$. The global emission uniformity is the product of these two parts. Previously, a formula was developed to predict the manufacturing emission uniformity by assuming that when the emitter is tested at a given head, emitter discharges are normally distributed around their mean. This assumption did not apply well to the tested emitters. In this research, the manufacturing part was expressed in terms of the statistical characteristics of the distribution of emitter discharges when tested at a given pressure head. The hydraulic part of emission uniformity, ${\mathrm{EU}}_h$, was expressed in terms of the hydraulic characteristics of the subunit. Many design cases were executed and for each design the matrix of emitters discharges and the hydraulic emission uniformity were calculated. The hydraulic emission uniformity was calculated by using the developed formula. The results obtained from the two methods were found to be closely related. The research involved conducting two sets of experimental work to test several types of emitters and the second set of experiments involved measuring actual emission uniformity of trickle irrigation systems to verify the theoretical formulas to calculate design emission uniformity. From the conducted experiments and the theoretical analysis it was found that for the tested emitters the distribution of emitter discharges, when tested at the same pressure head, around their mean was not normal; it is sufficient to test the emitter at a given head. The values of field emission uniformity were very close to those calculated by an existing and a developed formula. The developed formula provides a simplified method to calculate the hydraulic emission uniformity.

A numerical model of basin irrigation flow is a useful tool in the design and evaluation of surface irrigation systems. A two-dimensional (2D) complete hydrodynamic numerical model of basin irrigation was established by using the time–space hybrid numerical method. Differences in stability, convergence, precision, and efficiency of the 2D model were analyzed and compared between the hybrid numerical method proposed in this paper and the Roe finite-volume method. At the same time, the computational performance and simulation effects were validated on the basis of the results of typical basin irrigation tests. The results show that the hybrid numerical method provides better numerical stability and convergence with lower water quantity balance and average relative errors than does the Roe finite-volume method. The computational efficiency is about three times higher under the same measurement circumstances. The proposed model of basin irrigation can increase computational stability and convergence, improve computational precision and efficiency, and provide a good numerical simulation tool for the design and evaluation of basin irrigation systems.

When the flow in the capillary fringe above the water table is taken into account in land-drainage theory, water-table heights are lower than those predicted when incident rainfall on the surface is assumed to travel vertically through the vadose zone. An analytical solution is given here to the steady-state drainage problem of the flow of surface-incident rainfall to cylindrical drain channels for the situation of a completely tension-saturated soil above the water table. This gives the maximum effect that the unsaturated soil region above the water table can have on the water-table height for the given drainage system. Calculated results show that the water-table height above drain level is smaller for deeper drains below the soil surface and for larger drain radii than is the case when the effect of the capillary fringe is ignored. It follows that drainage design based on customary land-drainage theory ignoring the effect of a capillary fringe gives an overestimate for the drain spacing.

Many pumps are used for irrigation in central California, but a great number of them are operating inefficiently. In this paper, the information recovered from over 15,000 electric irrigation pump tests in central California is analyzed. The objectives of this study are to define the common characteristics attributed to pumps with best and worst performance and to identify the possible target groups that might benefit from improvements, obtaining potential energy savings. The results showed that pumps with lower reported total dynamic head (TDH) and flow rate ($Q$) usually have poorer overall pumping plant efficiency (OPPE) values, but high flow rates and input power are typically associated with better OPPE values. According to this analysis, energy savings of more than $100,000\mathrm{MWh}/\mathrm{year}$ could be achieved for well pumps, with a per-pump average of $50\mathrm{MWh}/\mathrm{year}$. For non-well pumps, the total potential savings are $16,500\mathrm{MWh}/\mathrm{year,}$ and the average per pump is $34\mathrm{MWh}/\mathrm{year}$.

Agricultural weather stations are normally utilized to register weather variables (e.g., temperature, relative air humidity, solar radiation and wind speed). These data can be used to estimate daily and hourly reference crop evapotranspiration ($E{T}_o$), which can provide important information for water resources optimization in irrigation scheduling. However, data captured by actual agricultural weather stations are not filtered, which may lead to a bad estimation of the parameters and consequently a deficient water management, endangering the horticultural crops. This paper presents the validation and filtering process for automagic agricultural weather stations (VIPMET), a new station that is endowed with a real-time data filtering process to ensure validation of the acquired data. In addition, the station can be remotely controlled for automatic data collection and management tasks through a 3G mobile router. A comparison between data registered by the station and data supplied by the nearest Murcian Agricultural Information Service (Spain) was carried out for evaluation purposes.

Good quality soil and water resources are often limited in arid and semi-arid regions; however, poor quality groundwater can be used conjunctively with good quality canal water to fulfill crop water demand in these areas. In the present study, a linear programming model was developed for the optimal land and water resources allocation to maximize net annual returns from a command area located in Jhajjar district of Haryana, India. The water production functions were developed and incorporated in the model to estimate the crop yield under different qualities of irrigation water. A groundwater balance constraint was imposed on the model, which mitigated the waterlogging problems while making optimal use of land and water resources. The model results show a reduction in rice and mustard areas against an increase in cotton, sugarcane, and wheat under optimal conditions. Under the optimal land and water allocation the groundwater use increases, which in turn mitigates the waterlogging and salinity problems of the command area. The net annual return from the command area increased by more than 20% under optimal allocations. The sensitivity analysis of the model parameters show that better price of crops is the most sensitive parameter followed by the crop area and cost of cultivation. State agencies and farmers involved in the actual agricultural production process are advised to practice conjunctive use of canal water and groundwater to maximize their farm income. This strategy could also mitigate further rise in the water table in the command area without installing expensive drainage systems, which is also not feasible because the groundwater quality is poor and the drainage water may pose a serious disposal problem.

Weather data measured in urban areas are generally more easily available than those in rural areas. If the urban weather data are used to calculate the reference crop evapotranspiration (${\mathrm{ET}}_0$) for rural irrigation management or spatial and temporal trend analysis, the results may be biased because of the differences in weather variables. We collected daily data for mean, maximum, and minimum temperatures; relative humidity; average wind speed; and sunshine duration from two stations: Kaifeng Station in the City of Kaifeng and Huibei Station in the nearby irrigation scheme for 1984–2009. ${\mathrm{ET}}_0$ for both stations were calculated using the FAO-56 Penman-Monteith method and then compared. The results indicated that the difference in daily ${\mathrm{ET}}_0$ was remarkable [with relative error (RE) of 52.6%], the difference between monthly average ${\mathrm{ET}}_0$ increased gradually during the last three decades and the temporal trends in annual average daily ${\mathrm{ET}}_0$ were opposite. There were significant differences in ${\mathrm{ET}}_C$ (with RE of 31.1%) and irrigation requirements (with RE of 24.3%) between the two stations. Even though the distance between the two stations is only 20 km, the urban weather cannot be used to estimate ${\mathrm{ET}}_0$ for rural irrigation management.

The test time, the time the failure occurred, and the service life of microsprayers of accelerated life tests are analyzed and compared with those of normal life tests on the basis of the life distribution and parameters determined by the test date. The feasibility of adopting an accelerated life test to improve the efficiency and durability of microsprayers is investigated accordingly. The testing time in the normal life test can be shortened by approximately 50% using the accelerated life test; the relative error in the service life estimation between the two tests is 1%–11%, and the relative error of the average service life estimation is 5% at different confidence levels. The estimation of the service life of a microsprayer obtained from the accelerated life test can substitute the result of the normal life test for reducing the test time under the condition of the error tolerance of the distribution parameters.