Journal of Irrigation and Drainage Engineering

The magnitude and driving forces of nocturnal evaporative losses, $E{T}_{c_{\mathrm{night}}}$, and the interactions of other surface energy fluxes and microclimatic variables under various climatic, soil, and management conditions are not well understood. Such relationships are important for ecophysiological studies. This research attempts to investigate such relationships. Furthermore, $E{T}_{c_{\mathrm{night}}}$ can be a sizable portion of the daily total evaporative losses. Most empirical equations, especially ones that use solar or net radiation to estimate daily evapotranspiration (ET), either ignore or poorly treat the contribution of $E{T}_{c_{\mathrm{night}}}$ to the daily total ET. Neglecting $E{T}_{c_{\mathrm{night}}}$ can lead to errors in determining the daily or the sum-of-hourly $E{T}_c$ (i.e., $E{T}_{c_{\mathrm{SOH}}}$) and can also cause cumulative errors when making long-term water balance analyses. In this paper, the magnitudes, trends, and contribution to the nocturnal surface energy balance of various microclimatic variables (air temperature, $T_a$; vapor pressure deficit, $VPD$; relative humidity, $RH$; and wind speed at 3 m, $u_3$) and surface energy fluxes ($E{T}_{c_{\mathrm{night}}}$; soil heat flux, $G$; sensible heat flux, $H$; and net radiation, $R_n$); were quantified and interpreted for a nonstressed and subsurface-drip-irrigated maize canopy. The effect of microclimatic variables and surface energy flux components on the Bowen ratio energy balance system (BREBS)-measured $E{T}_{c_{\mathrm{night}}}$ and daytime evaporative loss, $E{T}_{c_{\mathrm{day}}}$, were investigated in the growing season of 2005 (i.e., April 22–September 30) and 2006 (May 12–September 27). The nighttime evaporative losses were high early in the season during partial canopy closure because of increased surface soil evaporation and were also high later in the season during and after leaf aging, physiological maturity, and leaf senescence. The seasonal average nighttime evaporative losses for 2005 and 2006 were 0.19 and $0.11\mathrm{mm}/\mathrm{night}$, respectively. Losses of 0.50 mm or more occurred in 2005 and 2006 on eight and seven nights, respectively. The seasonal total $E{T}_{c_{\mathrm{night}}}$, $E{T}_{c_{\mathrm{day}}}$, and $E{T}_{c_{\mathrm{SOH}}}$ in 2005 were 31, 612, and 642 mm, respectively. The $E{T}_c$ values in 2006 were 16, 533, and 547 mm, respectively. In both years, the percent ratio of $E{T}_{c_{\mathrm{day}}}$ to $E{T}_{c_{\mathrm{SOH}}}$ usually was more than 80–85%. $E{T}_{c_{\mathrm{night}}}$ was affected primarily by $u_3$, $VPD$, and $T_a$. A strong relationship between $E{T}_{c_{\mathrm{night}}}$ and nighttime sensible heat was observed. Some of the largest ratios of $E{T}_{c_{\mathrm{night}}}$ to $E{T}_{c_{\mathrm{SOH}}}$ occurred on rainy nights with strong winds. Because of strong winds, the $E{T}_{c_{\mathrm{night}}}$ was high owing to the clear coupling among all energy exchanges within and above the canopy as a result of the mixing of the lower boundary layer of the microclimate. The results of this study showed that the $E{T}_{c_{\mathrm{night}}}$ can be up to 5% of the $E{T}_{c_{\mathrm{SOH}}}$, even for a subsurface-drip-irrigated maize canopy in which the soil surface is usually dry, thus, less evaporative losses potential compared with the surface or sprinkler-irrigated surfaces in which $E{T}_{c_{\mathrm{night}}}$ would be expected to be considerably higher because of wetter surface conditions. $E{T}_{c_{\mathrm{night}}}$ needs to be quantified for different vegetation surfaces and management practices, surface wetting, and climatic conditions to better account for nighttime water losses and better understand nighttime energy balance mechanisms.

This paper presents three models for the estimation of vapor pressure from temperature and humidity data as suggested by Food and Agriculture Organization (FAO) Irrigation and Drainage Paper No. 56 (FAO-56) that have been compared for their performance using daily data from 2002 through 2007 for a semiarid climatic region of Udaipur in Rajasthan, India. Vapor pressure data obtained from dew-point temperature has been used as actual vapor pressure. Model 1 performed better than the remaining two models. Lower values of vapor pressure are better modeled by the three models than higher values. The average absolute error of Model 1 varied from 5.09 to 15.59%, of Model 2 from 5.59 to 19.73%, and that of Model 3 from 5.62 to 37.21%. Estimates of vapor pressure obtained from the three models were also used to estimate open-water evaporation determined by the modified Penman method; the results were compared. Errors in vapor pressure data did not significantly affect estimates of evaporation, indicating that other factors such as energy budget played a much more significant role than mass transfer influence for this arid basin. Errors in evaporation estimation were $<4\%$ for Model 1, $<9\%$ for Model 2, and $<14\%$ for Model 3. Even for Models 2 and 3 they were $<6\%$ for most months. In general, Model 1 was found to be the best model of vapor pressure estimation and also caused the fewest errors in estimation of evaporation.

In many agricultural regions of the West, decades of intensive irrigation have produced shallow water tables under not only cultivated fields but also the nearby uncultivated land. It is possible that the high water tables under the uncultivated lands are substantially increasing evapotranspiration (ET) rates, which would represent an unnatural and potentially nonbeneficial consumptive use. The objective of this paper is to quantify loss of water that occurs from uncultivated lands in a semiarid irrigated river valley (the Lower Arkansas River Valley in southeastern Colorado). A remote-sensing algorithm is used to estimate actual ET rates on 16 dates on the basis of Landsat satellite images. On the same dates, water table depths, soil moisture values, and soil water salinities are measured at up to 84 wells distributed across three study sites. On the basis of a water balance of the root zone, it is estimated that 78% of the ET is supplied by groundwater upflux at these sites. It is also observed that the ET and groundwater upflux decrease with increasing water table depth. A regression analysis indicates that the spatial variations in ET are most closely related to variations in vegetation-related attributes, whereas soil moisture and water table depths also explain substantial amounts of the variation. Valley-wide implications for reducing nonbeneficial ET through water table control also are discussed.

The classical expressions obtained through the mathematical theory of friction head loss along the center-pivot lateral are adequate for many existing center-pivots. Nevertheless, several important aspects are not accounted for in the classic approaches, such as the presence of closed outlets at the beginning of the center-pivot and the friction head loss that occurs between the last sprinkler and the end gun. Furthermore, the irrigated radius and area considered in classical approaches are different from those used in this study. To address the previously mentioned important aspects, in addition to more standard situations, this paper develops closed-form expressions characterizing the friction head loss of center-pivot laterals with and without end-gun sprinklers and with and without closed outlets at the beginning of the center-pivot lateral. The friction head loss is computed by using two methods: continuous outflow distribution along the lateral using a different formulation from that in the literature, and discrete outflow distribution. Several applications are included that use the Chézy equation and the Hazen-Williams equation for both discrete and continuous distributions. The method of the discrete outflow distribution provides a closer description of the physical phenomenon and is used to validate the classical approaches. The formulas developed in this study validate the classical formulas for several practical applications. However, for a more accurate and general description of head losses, the approach developed in this paper is preferable because it produces more accurate results. These expressions, after small changes, can also be applied in multidiameter center-pivots, for laterals in which the spacing between outlets changes, and with ground slope.

Recently, Valiantzas proposed a new two-parameter vertical infiltration equation that can be transformed to a linearized-form equation that essentially states that the shape of the cumulative infiltration data, when presented in the form of ($i^2/t$) versus $i$, is linear. In this paper, the presentation of the numerical data to the Valiantzas linearized-form equation is proposed as an additional criterion to detect easily and rapidly possible errors of the numerical solutions and eventually to choose the best spatial discretization for a simulated infiltration event that is used as setup parameter to the numerical infiltration models. Numerical data and analytical solutions were used to validate the proposed method.

Reliable information about the wetted dimensions of soil under drip irrigation helps designers to determine optimal emitter flow rates and spacings to reduce system equipment costs and provide better soil water conditions for the most efficient and effective use of water. This study presents a new empirical formula that predicts soil wetted dimensions around a drip emitter. The coefficients were obtained by using regression analysis on the results of field experiments done on the Pardis Agricultural Farm of Tehran University in Karaj, Iran. These data were also used to evaluate the semiempirical model of Zur and Schwartzman, the empirical model of Amin and Ekhmaj, and the analytical model WetUp. Statistical comparisons (mean error, root mean square error, and model efficiency) are made of the simulated data with the observed data. To evaluate the models, published experimental data by Risse et al. and Li et al. were also used. The results demonstrate that the suggested equations can be used for a wide range of discharge rates and soil types. The best result was obtained from the new empirical model proposed in this investigation. The lowest mean error for the wetted radius and wetted depth was 8.21 and 8.62 cm, respectively.

This paper presents the results of an experimental investigation on flows inside stacked drop manholes (SDM). An SDM consists of two identical rectangular or square manhole chambers stacked together at an elevation difference. SDMs for different conditions were assessed on their ability to dissipate the energy of the approaching flow and their suitability to perform adequately under different flow conditions. Flow regimes were classified based on the inflow conditions and geometry of the structure in the first chamber and downstream outflows in the second chamber. An analysis based on the integral momentum equation was developed to estimate pool depths and energy losses under critical flow conditions. A fully surcharged stage with inflow and outflow pipes running full was also tested and velocity profiles were measured at a horizontal center plane to the opening connecting both shafts. Additionally, air flow rates were measured to assess the air demand into a large-height SDM.

In this paper, a quick surface infiltration test is presented for assessment of pervious concrete (PC) maintenance needs on small sites. Tests were conducted on PC sidewalk sections at Auburn University in Auburn, Alabama. Performance of a quick field infiltration test (QFIT) was compared with a modified double ring infiltrometer test (MDRIT). The more sensitive MDRIT results were used in the second part of the study to evaluate the effectiveness of two low-cost PC maintenance practices: (1) pressure washing and (2) pressure washing with power blowing. Results indicate both maintenance practices improved PC sidewalk infiltration rates an average 20-fold, with an almost 200-fold increase observed on sites cleaned by combined pressure washing and power blowing. Because the QFIT method can assess whether the PC pavement surface infiltration rate (SIR) is above or below $500\mathrm{cm}{\mathrm{h}}^{-1}$, this rapid, low-cost test can be recommended as an option for small-scale property owners to assess the need for pervious pavement cleaning relative to new unclogged pavement.

Population growth coupled with industrialization, increasing effects of climate change, and increasingly stringent water management regulations regarding the conservation of aquatic life are resulting in previously unknown agricultural water shortages in Padana Valley, Italy. To mitigate water shortage, it was recently proposed to use the water stored into numerous quarries of gravel material. Because quarry lakes are mostly located in the proximity of watercourses, aquifer drawdown induced by pumping can affect flow in nearby streams. The evaluation of the potential of quarry lakes for supplemental irrigation has to face stream depletion that is crucial from the perspective of the legal rights of the downstream users and ecosystem sustainability. The work presented in this paper investigates the potential of a quarry lake in Padana Valley to sustain irrigated crop water requirement during shortage periods. A simple and quite inexpensive technique for assessing streambed conductance based on streambed temperature measurements is presented. The results show that quarry lakes may be a promising alternative resource for supplemental irrigation during shortage periods, even when a watercourse is present in the surrounding area.