Journal of Irrigation and Drainage Engineering

This work studies the most beneficial way of allocating water in an irrigation community in water shortage situations. Therefore, it proposes that the irrigation surface area be divided into homogeneous zones, each with a beneficial relationship with respect to the water applied. The mathematical formula that enables one to obtain the optimal quota for the users or irrigation community as a whole has been found for individual relations of a quadratic or power type, and these have yielded different and complementary characteristics. Dimensionless variables have been used to display the results, and to compare with other alternative allocation rules such as the proportional rule, referencing the situation without water restrictions. As a result, for each water shortage situation, the water that is allocated to each user is obtained, together with the losses in individual income and the losses for the community as a whole. Furthermore, a proposal is put forth for establishing the marginal benefit from the water available, which could be of interest in enabling each community to analyze whether it is in its best interest to invest in increasing the resource, or to sell the resource to other users. Finally, an example is given to demonstrate how the method works and to show that, when the differences between the production schemes are considered, the differences in benefit reduction between the proportional allocation and the optimal allocation are also sizeable.

Nitrate (${\mathrm{NO}}_3^{-}\text{-}\mathrm{N}$) removal studies in rain gardens show great variability in removal rates, and in some cases ${\mathrm{NO}}_3^{-}\text{-}\mathrm{N}$ was exported. A three-way factorial design ($2\times 2\times 4$) was devised for eight outdoor unvegetated rain gardens to evaluate the effects of hydraulic loading (two sizes and two flow rates), the presence/absence of a buried wood chip layer (2), and the presence/absence of a subsurface saturated zone (SZ) (2) on nitrate-nitrite (${\mathrm{NO}}_3^{-}\text{-}{\mathrm{NO}}_2^{-}$) removal. Captured stormwater runoff was used in this study. Results showed that the presence of a SZ reduced the ${\mathrm{NO}}_3^{-}\text{-}{\mathrm{NO}}_2^{-}$ mass by 75% compared to a 7% reduction without this zone. The presence of a SZ significantly decreased ammonia-N (${\mathrm{NH}}_3\text{-}\mathrm{N}$) mass reduction ($p<0.00001$). The difference in total nitrogen (TN) mass reduction with the introduced SZ was not significant, largely due to ${\mathrm{NO}}_3^{-}\text{-}{\mathrm{NO}}_2^{-}$ mass reduction that was offset by ${\mathrm{NH}}_3\text{-}\mathrm{N}$ mass increases in rain gardens with the SZ. The buried wood chip layer showed no significant effect on N removal. No significant interactions were found between the factors. Overall, the results in this study highlight the importance of incorporating a subsurface SZ for ${\mathrm{NO}}_3^{-}\text{-}{\mathrm{NO}}_2^{-}$ load reduction and demonstrate that a buried wood chip layer as a carbon source did not make a significant contribution to N removal.

A suitable strategy for analyzing a water-resource system reaction to abrupt pollutants and for examining the necessity and the nature of management programs would necessitate quality-quantity modeling of the system and conflict-resolution methods to compromise between contradictory goals and desires. The allocation of drinking and agricultural water of the Karaj dam, one of the most strategic dams in Iran, is accomplished by using the CE-QUAL-W2 simulation model. In this study, an entering coliform pollution with ${10}^{13}\mathrm{mpn}/{\mathrm{m}}^3$ intensity is taken into account. In addition, a new conflict-resolution model is developed so that less water allocation is made based on the quality aspects desired. That is, poor quality water is allocated less, whereas more allocation is made along with an increase in the quality utility. Results show that, for abrupt pollution conditions, the developed quality-quantity model is 14% more suitable than the exclusion of water allocation. The present study with its developed methodology can be a guide for decision-makers to extract different reservoir allocations under abrupt pollution conditions.

Flumes and weirs are hydraulic structures used to measure soil erosion and runoff at the outlet of agricultural catchments. Long-throated flumes use critical flow theory to determine discharge from a single water depth measurement upstream of the flume structure. In erodible catchments, sediments often deposit at the entrance of the flume, just where water level is measured, preventing proper discharge determination. This work proposes the combination of critical depth theory with two models of water flow at free overfalls that may be applied when the exit of the flume presents a drop. The method allows the recording of discharge measurements when the upstream water level sensor fails because of the accumulation of sediments. This paper proposes three discharge predictors: (1) one based on critical flow theory, (2) another based on the momentum balance between the critical section and the free overfall section, and (3) the third based on energy balance between the upstream water section and the free overfall section. Two flume performance indicators and a practical protocol are used to decide, based on the performance indicators, which of the three discharge predictors is most appropriate for every flow situation. The critical flow discharge predictor is recommended when the performance indicators show evidence of no sediment deposition at the upstream section. On the contrary, the momentum balance discharge predictor is recommended if there is evidence of sediments deposition. In case of uncertainty, the recommended discharge predictor is the one based on energy balance between the upstream and the free overfall sections. The proposed equations apply to trapezoidal flumes, but they could be adapted for other geometries.

Field experiments were conducted on groundnuts (Arachis hypogea) at Rajkot, India, during kharif from 1996 to 2006 to assess the efficiency of four tillage treatments: (1) shallow ploughing, (2) deep ploughing every year, (3) deep ploughing alternate years, and (4) deep ploughing once every three years. The tillage treatments were assessed for their effects on rainwater use efficiency (RWUE), soil moisture at depths of 0–15 and 15–30 cm, cumulative depth of infiltration, pod and straw yields attained, and sustainability over the years based on the sustainability yield index (SYI) criterion. The rainfall received during the crop growing period (June to September) ranged from 210.9 to 1,119.5 mm with a mean of 582.4 mm and variation of 47.4% over the years. A significantly higher mean pod yield of $770\mathrm{kg}/\mathrm{ha}$ and a straw yield of $\mathrm{2,134}\mathrm{kg}/\mathrm{ha}$ were attained under yearly deep ploughing than under shallow ploughing (664 and $\mathrm{1,840}\mathrm{kg}/\mathrm{ha}$). Yearly deep ploughing resulted in a mean infiltration depth of 12.8 cm and a RWUE of $1.59\mathrm{kg}/\mathrm{ha}/\mathrm{mm}$, which were significantly higher than those of shallow ploughing (8.8 cm and $1.37\mathrm{kg}/\mathrm{ha}/\mathrm{mm}$). Regression models of pod and straw yield were calibrated through monthly rainfall received during June to September and cumulative rainfall of these four months to assess the sustainability of the models over the years. The models attained coefficient of determination values in the ranges of 0.41 to 0.53, based on monthly rainfall, and 0.71 to 0.76, based on cumulative rainfall, for predicting the pod and straw yields of groundnuts based on the long-term study. The SYI ranged from 19.7 to 24.8% based on monthly rainfall and 25.6 to 30.9% based on cumulative rainfall for attaining maximum pod yield, and from 35.7 to 40.5% based on monthly rainfall and 38.0 to 44.8% based on cumulative rainfall for straw yield. The deep ploughing done every year resulted in maximum gross returns of 22,661 Rupees per hectare with benefit-cost ratio of 1.53, compared to shallow ploughing, with 19,543 Rupees per hectare and 1.43, respectively. The study indicated that yearly deep tillage was superior to attain maximum groundnut pod and straw yields, SYI, RWUE, gross returns, and benefit-cost ratio, in addition to providing maximum depth of infiltration. The deep ploughing done every alternate year and every three years were found to be the second and third best treatments for different parameters based on the study.

The objective of the research reported in this paper was to determine the potential water-savings effectiveness of Toro Intelli-Sense evapotranspiration (ET)-based irrigation controllers in single-family homes. Of the 36 cooperators selected, 21 cooperators were outfitted with Toro Intelli-Sense TIS-612 (the ET group) and the remaining 15 were used as comparisons. The ET group reduced irrigation compared to the gross irrigation requirement by 23–41% and the 9-year historical average by 23–34%. Results varied based on the relationship between historical irrigation and the gross irrigation requirement, with water savings of 24%, no difference, and an increase of 54% when the historical value exceeded, approximated, and was less than the gross irrigation requirement, respectively. Turfgrass quality was maintained above an acceptable threshold for both treatments. In southwest Florida, a properly programmed Intelli-Sense controller is recommended when irrigation exceeds the gross irrigation requirement and at least 696 mm of irrigation is applied annually. Other smart-irrigation technologies would be more appropriate in locations for which the irrigation rate is less than the gross irrigation requirement.

Triangular weirs are commonly used to measure discharge in open channel flow, representing an inexpensive, reliable methodology to monitor water allocation. In this work, a low-speed photographic technique was used to characterize the upper and lower nappe profiles of flow over fully aerated triangular weirs. A total of 112 experiments were performed covering a range of weir vertex angles (from 30° to 90°), crest elevations (8 or 10 cm), and discharges ($0.01–7.82\mathrm{l}{\mathrm{s}}^{-1}$). The experimental nappe profiles were mathematically modeled and combined with elements of free-vortex theory to derive a predictive equation for the weir discharge coefficient. Comparisons were established between measured $C_d$, the proposed discharge coefficient equation, and discharge coefficient equations identified in the literature. The proposed equation predicts $C_d$ with a mean estimation error (MEE) of 0.001, a root-mean square error (RMSE) of 0.004, and an index of agreement (IA) of 0.984. In the experimental conditions of this study, this performance slightly improves that of the equation proposed by Greve in 1932, and showed the same absolute value of MEE but lower values of RMSE and IA.

The flow process of weirs of finite crest length is analyzed on the basis of the dimensional analysis and incomplete self-similarity theory. The crest length is incorporated in the functional stage-discharge relationship for weirs of finite crest length. The theoretically deduced stage-discharge formula was then calibrated using the experimental data compiled in this research. According to the current experimental data it is also concluded that the performance of the proposed stage-discharge formula is better than the previous dimensional stage-discharge formulae. Also, the proposed stage-discharge formula is applicable for all types of the weirs, i.e., long-crested, broad-crested, short-crested, and sharp-crested ones.