Journal of Irrigation and Drainage Engineering

It has been demonstrated that soil moisture sensor systems (SMSs) designed for landscape irrigation can save water. However, SMSs have not been tested with reclaimed wastewater. Both salts contained in the irrigation water and temperature might alter the soil water content (SWC) sensed by SMSs. The objective of this research was to quantify the effect of salinity and/or temperature on the precision and accuracy of three different commercially available SMSs. The brands, controllers, and probes selected for this experiment were as follows: Acclima, SCX, and Digital TDT, Baseline, WaterTec S100, and biSensor, and Dynamax, IL200-MC, and SM200. Every SMS was replicated three times. Each SMS probe was installed in the center of different containers filled with an Arredondo fine sand. The containers were placed in a controlled-temperature chamber and were saturated and dried down across a combination of three temperatures (10, 25, or 35°C) and three electrical conductivities (0, 0.7, or $5\mathrm{dS}/\mathrm{m}$). Each container was placed on a platform scale to determine soil water losses, by weight variation over time. The actual or measured SWCs were then compared with their respective SMS readings. A regression analysis was performed, per brand, for each combination of salinity and temperature. Acclima resulted in the most robust and reliable system, with no practical reading variations when exposed to different combinations of temperatures and salinities. Both Baseline and Dynamax systems were sensitive to high salinity and/or high temperature, making their use more difficult in extreme or changing situations. However, all tested SMSs followed with adequate precision the SWC under the different salinity and temperature scenarios. Consequently, these SMSs might achieve an adequate landscape irrigation control, even when their readings might not correspond to the actual SWC.

The soil moisture flow and solute transport regimes of the vadose zone associated with specific hydrogeological conditions play a crucial role in pollution risk assessment of the underlying groundwater resources. An effort has been made to map the vulnerability of shallow groundwater to surface pollutants of Doon Valley, an intermontane watershed in North India situated between the lesser Himalayas and Shiwalik ranges, using soil moisture flow and contaminant transport modeling. The classical advection dispersion equation coupled with the Richard’s equation is numerically simulated at different point locations for assessing the intrinsic vulnerability of the valley. The role of soil type, slope, and land-use cover is considered for estimating the transient flux at the top boundary from daily precipitation and evapotranspiration data of the study area. The time required by solute peak to travel from the surface to the groundwater table at the bottom of the soil profile is considered as an indicator of vulnerability index. Results show a high vulnerability in the southern region, whereas low vulnerability is observed in the northeast and northern parts of the valley. These findings are in line with the observed low water table depths, less runoff, and higher hydraulic conductivity of the vadose zone material in the southern part of the valley. The study may assist in decision making related to planning of industrial locations and the sustainable water resources development of the valley.

Lysimetric experiments were conducted in order to investigate the effects of saline shallow groundwater on water requirements and other parameters of coriander plant in a semiarid climate. The plants were grown in 27 columns each with a diameter of 0.40 m and packed with silty clay soil. The experiments were carried out with three replicates using a randomized complete block design with different treatment combinations. Nine treatments were applied in each experiment by maintaining groundwater with an EC of 1, 2 and $4{\mathrm{dSm}}^{-1}$, at three different water table levels of 0.60, 0.80, and 1.10 m. The supplementary irrigation requirements for each treatment were applied by adding surface water with EC of $1{\mathrm{dSm}}^{-1}$. The results of experiments showed that for groundwater qualities 1, 2 and $4{\mathrm{dSm}}^{-1}$; and water table depths 0.60, 0.80, and 1.10 m, the average percentage of groundwater contributions were to be 66.6, 55.3, and 46.3%; 59.2, 50.8, and 40.3%; and 49.3, 37.3, and 27.3% of the average annual coriander water requirements, respectively. The results indicated that coriander is a medicinal plant that is sensitive to salinity.

Adequate analysis of lateral hydraulics is a very important concern for the design and evaluation of microirrigation systems. One of the main tasks of the lateral hydraulic calculation is to determine the pipe geometric characteristics (pipe size and length) with the required operating inlet pressure head, and the total friction head losses along the lateral line, assuming that the total flow rate at the inlet, characteristics of the emitter, and the acceptable level of uniformity are known in advance. This paper aims to present an efficient computer program in Visual Basic 6.0, named “Multi-flowCAD,” which is based on a stepwise computation algorithm for determining the hydraulic design variables (pipe size, pipe length, and operating inlet pressure head) and the hydraulic flow characteristics (emitter outflow-pressure head distribution, lateral discharge, and total friction losses) along the energy-grade line. The stepwise algorithm takes into account the velocity head change and variation of the Reynolds number, which affects the selection of the proper friction coefficient formula to be applied along the different reaches of the pipeline, whereas some additional minor local losses resulting from emitter connections are neglected. An illustrative example of determining the operating inlet pressure head by a trial-and-error-procedure to achieve the design criteria (initial and boundary conditions) is presented. For any desired uniformity level, the procedure also provides an opportunity to evaluate the influence of different uniform line slopes on the pipe geometric characteristics (pipe size and length) and on the corresponding hydraulic variables (required operating inlet pressure and downstream-end pressure heads and total friction head losses). On the basis of the computer outputs, variations of the operating inlet pressure head, total friction head losses, and uniformity coefficients depend on the examined pipe lengths ranging between 25 and 250 m and the internal diameters ranging between 10 and 21 mm in the horizontal pipe case, and were depicted graphically in dimensionless form for practical purposes. The present software technique was implemented successfully with the highest degree of accuracy because only the basic equations of the hydraulics of steady-state pipe flow condition were sensitively used in each pipe section between successive outlets. Examinations of various design configurations clearly showed that the performance of the Multi-flowCAD is satisfactory, and its results are in close agreement with those obtained by previous research.

This work presents a simplified probabilistic-topologic model for reproducing rill network surface runoff on a square-plane hillslope. The model requires only two parameters: the first is related to the production capacity of overland flow of the hillslope, at the initial conditions of the process, and the second depends on the sinuosity of the rill network. From a hydrological point of view, the following parameters account for the effects that essentially delineate the hydrologic response of a natural hillslope: rainfall intensity, hillslope roughness, and slope. Obviously, the reliability of the model is pending experimental validation that has only just begun. However, a preliminary experiment conducted on a $1.0\times 1.3\text{-}\mathrm{m}$ test plot, with variable slope, has produced promising first results.

Inflow cutoff, or turning off water inflow to an irrigated field based on water advance location downfield, is commonly used by irrigators as a means of reducing tail discharge (runoff) during surface irrigation of forage and range crops. To apply a scientifically sound cutoff strategy using a calculated inflow cutoff time or cutoff advance location, multiple field parameters (e.g., water inflow rate, rate of water advancement) need to be measured using multiple (potentially expensive) sensors and instrumentation. In this study, a sensor-based irrigation inflow cutoff strategy for surface irrigation was developed that deploys simple wireless contact-type sensors to measure wetting-front arrival time and surface water depth along a border check during the advance phase. These data were coupled with a multi-irrigation volume balance model (i.e., separate model parts for initial and subsequent irrigations of growing season) to determine appropriate cutoff times and/or locations, based on user-defined runoff and approximations of inflow rates and infiltrated depths. The model was verified using the field data collected during irrigation of a border-irrigated alfalfa field near Davis, California. The inflow rate corresponding to the initial (i.e., first of a growing season) irrigation event was within a 95% confidence interval of the measured inflow rates for all subsequent irrigations, in which identical irrigation setups were maintained. Moreover, a correlation between model approximated and reference infiltration depths was found with a coefficient of determination value ($R^2$) of 0.91. These parameters are necessary to calculate an inflow cutoff time during irrigation. Field-collected data confirmed that a combination of sensors and the model-based approach can provide a practical and valid technique for better managing tail runoff in surface-irrigated fields without the need for individual measurements using external equipment (e.g., inflow measurement using flow meters).

Effective sprinkler irrigation for cold protection requires an adequate and uniform water application rate (AR) in order to provide enough heat by freezing to compensate for heat loss by other means (i.e., evaporation). Several models have estimated the sufficient AR for cold protection as $6.35\mathrm{mm}/\mathrm{h}$; however, this value has little field verification. The objective of this study was to evaluate the effect of sprinkler type, sprinkler spacing, and water supply pressure under varied wind conditions on low quarter irrigation distribution uniformity ($D{U}_{lq}$) and AR. Distribution uniformity was tested using four sprinkler types (Wade Rain WR-32 and Nelson: R33, R33LP, and R2000WF) assessed at three pressure levels (345, 276, and 207 kPa), two sprinkler spacings (14.6 and 12.2 m), and varied wind conditions ranging from low ($0.2\mathrm{m}/\mathrm{s}$) to high ($7.2\mathrm{m}/\mathrm{s}$). The interactions (1) sprinkler type–pressure, (2) sprinkler type–spacing, and (3) pressure-spacing resulted in a significant effect on $D{U}_{lq}$ and AR, as well as, the effect of wind speed, which was included as a covariate in the analysis. The R2000WF and WR-32 sprinklers at 345 kPa and 12.2 m spacing resulted in the highest uniformity, and by contrast, obtained the lowest AR when evaluated at 207 kPa and 14.6 m spacing. Overall $D{U}_{lq}$ did not differ drastically across the factors tested, whereas AR was substantially impacted by these factors. Current strawberry growers systems are set up at 14.6 m sprinkler spacing with $2–3\mathrm{mm}/\mathrm{h}$ AR, which is substantially lower than the recommended AR of $6\mathrm{mm}/\mathrm{h}$ and may result in inadequate cold protection. Using manufacturer recommended spacing with commonly used sprinklers (WR-32) would result in $4–5\mathrm{mm}/\mathrm{h}$ AR depending on supply pressure available; hence, a greater level of cold protection.

In soilless culture, irrigation scheduling is an important and difficult task, as water and nutrients must be frequently and precisely applied, due to the reduced volume and low water holding capacity of most of the substrates. This paper describes an efficient control system for irrigation management of soilless culture based on an irrigation tray and a new adaptive hybrid automatic irrigation control algorithm. The proposed irrigation scheduling criteria are based on applying constant amounts in every irrigation application and variable timing as a function of crop water consumption. The control system analyzes the water balance in the control tray from the information provided by the sensors on the measured inputs and outputs of water from the tray. A hybrid algorithm composed of two stages is proposed. An estimation of the irrigation interval between irrigations is made by using an average daily crop water uptake pattern obtained from the feedback information of the tray. Short-term variations of the crop water uptake from the average daily pattern are adjusted by applying a proportional-integral (PI) controller. A field test was conducted to assess the performance of the proposed control system. The irrigation controller performed reasonably well as it fitted the leaching fraction for most of the irrigation events to the target value and its productive results were comparable to the ones obtained in a radiation-based control treatment.

The side sluice gate is used in open channels to divert a part of flow to a side channel and to regulate the head of distributaries. In present study, the distribution of the three-dimensional velocity in the vicinity of the side sluice gate was obtained using an acoustic Doppler velocity meter (ADV). The structure of each component of velocity was separately examined. The velocity distributions indicated that longitudinal velocity peaks near the beginning of the side gate, whereas velocity in the direction of side channel and vertical velocity are highest at the middle of the side gate. In the vicinity of the side gate, the direction of the vertical velocity is downward. In the section area of the side gate, the diversion angle of velocity vectors in the horizontal plane is increased with increasing the distance from the beginning of the side gate. It reaches to the maximum value at the end of the side gate.