Journal of Irrigation and Drainage Engineering

Chufa, also known as tigernut, is a typical crop in Valencia, Spain, where it is cultivated in ridges with furrow irrigation. This paper examines the effects of the planting strategy (PS) and irrigation system (IS) on yield and irrigation water use efficiency (IWUE) on the basis of the results from a two-year study. The authors analyzed three PS, ridges with a plant row (R) and flat raised beds containing two (B2) or three (B3) plant rows and compared two IS, furrow (FI) and drip irrigation (DI). Irrigation was based on the volumetric soil water content (VSWC), continuously monitored with capacitance sensors. Each irrigation event started when the VSWC in R dropped to 60 or 80% of the field capacity in FI or DI, respectively. Beds and ridges were irrigated simultaneously and for the same duration. There were differences among IS and PS, with DI and B2 obtaining the highest yield. On average, DI produced higher IWUE values than FI; the highest IWUE was obtained in R for DI, and the lowest IWUE was obtained in R for FI. Thus, modifications to the PS and the IS in chufa cultivation will increase IWUE and lead to major water savings.

Because water diverted from the Yellow River has been used for irrigation in 1972, obvious changes in evapotranspiration demand (denoted by reference evapotranspiration) have been observed in the Jingtai Irrigation District, Northwest China. Increasing irrigation-water consumption corresponding to irrigation expansion led to less local evapotranspiration demand after 1972. The crop and irrigation-water requirements per unit area were influenced by the changes in evapotranspiration demand. A simple prediction approach based on the complementary relationship of evapotranspiration was used to estimate the irrigation-induced changes in evapotranspiration demand and their influences on irrigation-water requirement. Future variations in net irrigation requirement per unit area under different irrigation scenarios at 50% and 75% precipitation levels were evaluated. Irrigation requirements per unit area would decrease under irrigation-expansion scenarios but increase under irrigation-reduction scenarios corresponding to the irrigation-induced changes in evapotranspiration demand. Irrigation-induced local changes in evapotranspiration demand should be seriously considered for irrigation planning and management.

Water movement in the soil–root system is an important component in modeling of the hydrological processes. A nonlinear root uptake model was developed and validated for a nonuniform crop root zone in a semiarid agro-climate. The developed model is based on a fully implicit finite difference scheme. Field experiments were conducted on a maize (Zea mays) crop for prediction of moisture uptake pattern. Model moisture uptake prediction efficiency was analyzed on the basis of experimental data collected from the field for nonuniform/multilayer vis-à-vis uniform crop root zone. Model predicted soil-moisture parameters, i.e., moisture depletion, moisture status at various depths, and soil moisture profile in root zone, are in good agreement with experimental results. The simulated moisture prediction has good agreement with observed values in multilayer soil depth as compared to uniform soil depth. The results emphasized the utility of the water uptake model across different agro-climates and established its efficacy for nonuniform soils having variations in soil moisture properties along depth in predicting soil moisture in crop root zone.

There are several studies that have estimated how much water is used for residential irrigation, principally at the national level, with outputs varying from 30 to 64% of total household potable water use. A methodology to estimate irrigation from potable use data in central Florida is presented in this paper. Monthly potable water billing records of single-family homes for the City of Tampa Water Department (TWD) and Orange County Utilities (OCU), Florida, were available from 2003 to 2007. Basic indoor water use at the household scale was estimated using two methods: the minimum month method and the per capita method. A range of impervious surfaces values (5, 15, and 20% from total green area) was considered to estimate the irrigable area. Irrigation was estimated on a monthly basis as the difference of total water use minus the estimated indoor water use, divided by the irrigable area. The estimated irrigation values were compared to a monthly theoretical irrigation requirement calculated by a daily soil water balance. The average total potable water use was 29.2 and $53.3{\mathrm{m}}^3/\mathrm{month}$ in TWD and OCU, respectively. The basic indoor water use ranged from 15.7 to $35.9{\mathrm{m}}^3/\mathrm{month}$ in TWD and OCU, respectively, based on the minimum month method, and from 16.9 to $18.3{\mathrm{m}}^3/\mathrm{month}$ when the per capita method was used. Some inaccuracy in the minimum month method was detected, at least for OCU, and the per capita method would be better for estimating indoor water use. Our results showed that 57–62% and 45–64%% of homeowners overirrigated in OCU, with an estimated irrigation amount of 104–62 mm/month when the per capita method and the minimum month method were used, respectively. In TWD, 31–36 to 22–27% of homeowners overirrigated when the per capita method and the minimum month method were used, with averages of 54 and $31\mathrm{mm}/\mathrm{month}$, respectively. The minimum month method showed the lowest estimated values on irrigation compared to the per capita method. Further work is needed to determine which indoor use method is most accurate.

In this study, a SIMulation of EvapoTranspiration of Applied Water (SIMETAW) model was evaluated using monthly climatic data of four stations in Iran, namely Bushehr, Tabriz, Zahedan, and Mashhad, to investigate the effects of climate change on reference evapotranspiration (${\mathrm{ET}}_o$). SIMETAW generates daily weather data from monthly values applicable in climate change studies. HadCM3 (Hadley Centre Coupled Model ver.3) outputs were statistically downscaled to project future variables. Maximum, minimum, and dew point temperature, precipitation, and wind speed were downscaled under two emission scenarios (A2 and B2) and two future periods (2020–2050 and 2050–2080) to simulate ${\mathrm{ET}}_o$. Calculated ${\mathrm{ET}}_o$ values were compared with those simulated by SIMETAW in the base period (1961–2000). Results showed that, except for daily wind speed, the model accurately generated daily temperature variables and monthly precipitation. Furthermore, ${\mathrm{ET}}_o$ is expected to increase in most months. Values of ${\mathrm{ET}}_o$ at Bushehr Station are projected to increase from 164.7 to $181.2\mathrm{mm}/\mathrm{month}$ in 2050–2080, under the B2 scenario. The corresponding values are 125.4 to 137.5, 182.7 to 197.5, and 118.3 to $128.8\mathrm{mm}/\mathrm{month}$ for Tabriz, Zahedan, and Mashhad, respectively.

The rational method is derived as a special case of kinematic wave flow. The definition of runoff coefficient is expanded from the peak-based to volume-based ratio between runoff hydrograph and rainfall hyetograph. The new method presented in this paper provides a dimensionless approach to derive the runoff coefficients for the conventional two-flow drainage system and the low-impact cascading drainage systems. The key factors for the determination of runoff coefficients were identified as the ratios of depression loss and infiltration amount to the design rainfall depth. Although this method provides theoretical values for runoff coefficients, field data or computer simulation are always helpful for further validation.

Urban storm water runoff carries particulate matter and other pollutants to water bodies, causing environmental problems. Removing suspended solids from runoff through geotextile filtration is a storm water control measure currently under investigation, which could help lessen the negative impacts of storm water on aquatic ecosystems. In this study, three geotextiles were tested in a laboratory setup with influent suspensions having hydraulic loading rates, total suspended solids (TSS) concentration, and particle-size distributions similar to those reported for urban highway storm water runoff. The results indicated that after a short priming period, all three geotextiles can effectively remove suspended solids to below a target concentration of $30\mathrm{mg}/\mathrm{L}$. The results also showed that influent hydraulic loading rate and TSS concentration have minimal effects on the total mass of solids captured by the filter, whereas particle-size distribution does affect the total mass of solids captured by the filters. The retention criteria for choosing the appropriate geotextile for storm water treatment established in recent literature were evaluated by using the laboratory results. The geotextiles and sand filters were directly compared by using the results of the laboratory column testing of sand filters performed for this study. The results indicate that a geotextile will outlast a sand filter in terms of total solids loading under similar conditions.

Discharge through circular culverts under inlet control can be calculated using several empirical and theoretical methods; however, most methods require knowledge of site-specific characteristics, and some may even require that a rating curve be developed for each individual culvert. This process is onerous and often too time-consuming for land managers. The objective of this study was to identify a simple and accurate method to determine discharge at culverts. In this study, discharge at culverts was measured in forested watersheds using trapezoidal flumes and salt tracer tests and compared to discharge estimated using theoretical and empirically derived equations. The equation that best estimated culvert discharge was determined. This equation requires two variables: the diameter of the culvert and the height of the water at the culvert inlet. While this study used capacitance devices to measure and record stage at the culvert inlet, simple staff gauges or crest gauges could be used to measure water height adequately and subsequently calculate discharge from culverts.

In semiarid cold desert climates, bioinfiltration gardens as green infrastructure storm-water management facilities show promise to serve as both on-site storm-water management and no-irrigation landscaping. Both services must be demonstrated for bioinfiltration to be considered green infrastructure, because most urban centers in cold desert climates in the western United States (e.g., Salt Lake City, Utah; Boise, Idaho; and Denver, Colorado) must import water from the Colorado River for landscape irrigation, radically changing local and regional hydrology. To verify that storm-water runoff can sustain properly selected plants, we installed soil moisture sensors in a bioinfiltration garden in a cold desert climate with a contributing impervious area to garden area ratio of $1:1$ and monitored soil water for one summer. In spite of the small contributing impervious area, we found that the minimum soil water potential ($\psi$) observed was $-2.5\mathrm{mPa}$. Plants native to cold desert climates often do not show signs of water stress until $\psi$ drops below $-5\mathrm{mPa}$, indicating the selected plants did not experience water stress in this study. We conclude that with proper site design and plant selection, plants in bioinfiltration gardens can be sustained solely by runoff. If the bioinfiltration gardens are constructed in fall, winter, or spring, no irrigation will likely be needed for establishment.