Discharge Coefficient Analysis for Triangular Sharp-Crested Weirs Using Low-Speed Photographic Technique

Abstract 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  l 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 Cd, the proposed discharge coefficient equation, and discharge coefficient equations identified in the literature. The proposed equation predicts Cd 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

Estimating Potential Evapotranspiration by Missing Temperature Data Reconstruction

This work studies the statistical characteristics of potential evapotranspiration calculations and their relevance within the water balance used to determine water availability in hydrological basins. The purpose of this study was as follows: first, to apply a missing data reconstruction scheme in weather stations of the Rio Queretaro basin; second, to reduce the generated uncertainty of temperature data: mean, minimum, and maximum values in the evapotranspiration calculation which has a paramount importance in the manner of obtaining the water balance at any hydrological basin. The reconstruction of missing data was carried out in three steps: (1) application of a 4-parameter sinusoidal type regression to temperature data, (2) linear regression to residuals to obtain a regional behavior, and (3) estimation of missing temperature values for a certain year and during a certain season within the basin under study; estimated and observed temperature values were compared. Finally, using the obtained temperature values, the methods of Hamon, Papadakis, Blaney and Criddle, Thornthwaite, and Hargreaves were employed to calculate potential evapotranspiration that was compared to the real observed values in weather stations. With the results obtained from the application of this procedure, the surface water balance was corrected for the case study

Use of the Kalman Filter for the Interpretation of Aquifer Tests Including Model and Measurement Errors

The hydraulic parameters representative of actual aquifer conditions can be obtained through aquifer tests formerly known as pumping tests. Diverse methodologies based on analytical or numerical solutions have been proposed for the interpretation of aquifer tests; however, measurement and model errors are often neglected, which could lead to hydraulic parameter values that do not reflect the aquifer conditions. In this paper, a new alternative is presented for the interpretation of aquifer tests in confined aquifers based on the Cooper–Jacob solution by means of the dynamic Kalman filter and a nonlinear optimization method. This proposal was tested in two previously published case studies; the measured drawdowns were filtered by considering measurement and model errors to match the Cooper–Jacob solution. For the case studies, the results show that filtering the measured drawdowns leads to variations of up to 49.97% in the values for T and 150% for S when compared to the values determined by methodologies that neglect measurement and model errors. A poor match between filtered and measured data reflects large measurement errors and considerable deviations of the aquifer conditions with respect to the proposed model

Método para el diseño óptimo de redes de monitoreo de los niveles del agua subterránea

Para estimar la disponibilidad del agua subterránea y su evolución es indispensable medir los niveles del agua subterránea por periodos largos de tiempo. Sin embargo, los recursos económicos son una limitante en la recopilación de suficientes datos que permitan estimar con certeza la evolución de dichos niveles. Por este motivo se requiere de métodos para el diseño de redes de monitoreo de los niveles del agua subterránea que faciliten utilizar los recursos económicos disponibles para el monitoreo de manera efectiva. El método de Herrera y Pinder (Herrera, 1998) para el diseño óptimo de redes de monitoreo de la calidad del agua subterránea, aplicado por Herrera et al. (2001), y también por Herrera y Pinder (2005), tiene varias ventajas. Por un lado, permite seleccionar tanto posiciones como tiempos de monitoreo en forma óptima; además, con la información obtenida de la red de monitoreo, permite hacer estimaciones en espacio y tiempo, y utiliza un modelo de flujo y transporte, el cual sintetiza el conocimiento de las características del acuífero, de la dinámica del flujo subterráneo y de la problemática de calidad del agua subterránea que se tenga, así como del conocimiento de las leyes de la física. En este trabajo, una modificación de esta metodología se prueba por primera vez para el diseño de redes de monitoreo de los niveles del agua subterránea. Se presenta un caso sintético en el que la red se diseña para un solo tiempo, suponiendo que el flujo está en estado estacionario. Los resultados presentados indican que la metodología propuesta por Herrera y Pinder para el diseño de redes de monitoreo tiene buenas perspectivas para aplicarse exitosamente al diseño de redes de monitoreo de los niveles del agua

Non-Linear 3D Satellite Gravity Inversion for Depth to the Basement Estimation in a Mexican Semi-Arid Agricultural Region

In Mexico, agriculture in semi-arid regions is highly dependent on groundwater resources, where most of the aquifers’ characterization is a pending task. In particular, the depth to the basement is unknown for most of the Mexican territory. Hence, the development and performance of new techniques for the basement relief estimation is imperative for further hydrogeological studies. In this paper, we present a depth to the basement estimation using non-linear gravimetric inversion employing satellite data. Gravity forward modeling was implemented using both gravitational attraction due to juxtapositioned blocks and gravimetric non-linear inversion using conjugate gradient least squares to minimize the objective function in terms of a depth model. All of this took place under the sparse system framework. We present a synthetic result using the SEG-Bishop depth model taken for calibration purposes. Then, we recollected gravity data from The Satellite Geodesy group from SCRIPPS for the depth to the basement estimation of an unconfined aquifer in the northern-central semi-arid region of Zacatecas, Mexico. Both synthetic and satellite data were recovered, consistent depth models for both cases were presented, and a comparison with conventional gravimetric linear inversion for density estimation was performed

Evaluation of Groundwater Quality for Human Consumption and Irrigation in Relation to Arsenic Concentration in Flow Systems in a Semi-Arid Mexican Region

The supply of drinking water to the population is an important challenge facing humanity, since both surface and underground sources present a great variability of water storage with respect to space and time. This problem is further aggravated in arid and semi-arid areas where rainfall is low and torrential, which makes groundwater the main source of supply; therefore, it is necessary to carry out studies that allow evaluating the evolution of the quantity and quality of water. This study addresses the behavior of groundwater in a semi-arid region, considering the theory of flow systems to identify movement as well as water quality, es determined by a water quality index (WQI), calculated considering arsenic and fluorine. In addition, a quality irrigation classification is used, employing the norms in accordance with international standards and the Mexican Norm, which allows for a comparison. Local, regional, intermediate and mixed flow systems are identified, and the evolution of cations and anions in addition to temperature is examined. It is observed that the drinking water quality index classifies them as excellent in most of the monitored wells (<50), but with a negative evolution. Regarding irrigation, most of the water samples are classified without restriction for the establishment of any type II crop (C2S1) and with restrictions for horticultural crops. It is observed that arsenic had values between 0.49 and 61.40 (µg/L) in 2005, while in 2015 they were between 0.10 and 241.30 (µg/L). In addition, fluoride presented values between 0.00 and 2.6 (mg/L) in 2005, while in 2015 they were between 0.28 and 5.40 (mg/L). The correlations between arsenic and fluorine are noted as well as WQI and SAR. A finding in this research was to include arsenic and fluorine in the calculation of the WQI allowing a better interpretation of the quality of water for both human consumption and for agricultural use to based on this make the best decision to control any harmful effects for the population, in addition to identifying the appropriate purification treatment required to control pollutants. It is concluded that arsenic is an element of utmost importance when considering water quality, so it is necessary to examine its evolution and continue to monitor its levels constantly

Teaching Sprinkler Irrigation Engineering by a Spreadsheet Tool

Since being released 40 years ago, computer spreadsheets have proven to be worthwhile for use in educational contexts. There is plenty of evidence for this in practically every scientific discipline and engineering field. In view on this fact, the present work exposes a didactical resource, named the sprinkler irrigation tool, developed in Excel® spreadsheet licensed by 2018 Microsoft©. The objective of this tool is to offer an alternative to students in irrigation engineering, particularly for those training in the design of sprinkler irrigation systems so they can develop their theoretical knowledge and practical skills acquired in laboratory and field experiments. The main findings reported in this paper address well-agreed methodologies for evaluating radial patterns of precipitation rates, diameter distribution frequency, ballistic simulation of water drops’ movement through air, kinetic energy, and performance indicators as part of the core parameters of efficient irrigation system management. This computing tool provides outcomes in tabular and graphical formats that are consistent with those found in studies previously published in specialized literature on related topics. Likewise, spreadsheets have been proven to be adequate pedagogical instruments on the path to achieving meaningful learning; however, this assertion still needs to be confirmed through a rigorous study of students who have used the developed tool

Design of Groundwater Level Monitoring Networks for Maximum Data Acquisition at Minimum Travel Cost

Groundwater monitoring networks represent the main source of information about water levels and water quality within aquifers. In this paper, a method is proposed for the optimal design of monitoring networks to obtain groundwater-level data of high spatial relevance at a low cost. It uses the estimate error variance reduction obtained with the static Kalman filter as optimization criteria, while simultaneously evaluating the optimal routes to follow through the traveling salesman problem. It was tested for a network of 49 wells in the Calera aquifer in Zacatecas, Mexico. The study area was divided into three zones, and one working day (8 h) was taken to visit each one, with an average speed of 40 km/h and a sampling time of 0.5 h. An optimal network of 26 wells was obtained with the proposal, while 21 wells should be monitored if the optimal routing is neglected. The average standard error using 49 wells of the original network was 35.01 m, an error of 38.35 m was obtained for 21 wells (without optimal routing) and 38.36 m with the 26 wells selected using the proposal. However, the latter produce estimates closer to those obtained with the 49 wells. Following the proposal, more field data can be acquired, reducing costs

Upward Trends and Lithological and Climatic Controls of Groundwater Arsenic, Fluoride, and Nitrate in Central Mexico

Central Mexico is known for its high concentrations of geogenic arsenic (As) and fluoride (F−) in the groundwater; however, concentrations vary widely within the region. To identify specific hydrogeological processes that cause these variations, the study area was divided into four sections, each section with a particular lithology, climate, and land use. Nitrate was added to the analysis as a common anthropic contaminant in this area as one that is indicative of human and agricultural activities. Concentration maps, Na-normalized diagrams, Spearman correlation, and upward trend analyses were applied to 77 wells distributed across the four sections. Specific patterns of concentration emerged according to climate and the lithology of the exposed rocks. A sharp reduction of F− concentrations in the section where carbonate rocks outcrop suggested co-precipitation of F− with calcite. The Mann–Kendall method detected upward trends in 5 out of 54 wells for As and NO3–N and three for F− at a 95% probability level. Several wells with upward trends of As and NO3–N overlapped. Only one well showed a downward trend for NO3–N. The results show the degree to which lithology and climate affect groundwater quality, information that leads to a better understanding of the processes (and health hazards) that govern As, F−, and NO3–N concentrations, which could be construed to include the potential effect of human activities such as overfertilization and altering groundwater residence time via groundwater withdrawals

Improving the Water-Use Efficiency and the Agricultural Productivity: An Application Case in a Modernized Semiarid Region in North-Central Mexico

The increasing population demands a greater quantity of food. In order to satisfy the world’s demand, one of the main challenges worldwide consists of modernizing the current irrigation systems. This research shows an experience carried out in a modernized irrigation module in Central-North Mexico following these objectives: to evaluate the impact of the modernization of the irrigation module, to analyze the agricultural productivity, and to assess a group of parameters related with the agricultural production (system conduction and distribution efficiencies, water productivity, among others) and the water volumes after and before the modernization. After a drought period, a methodology was performed in commercial parcels in 2013 to increase the yield of different crops. Some of the activities were: soil leveling, estimation of the soil properties (field capacity, wilting point, bulk density, pH, and organic matter), optimum fertilization applications, use of a model to scheduling irrigation, measure volumes extracted at the parcel level. With the modernization and the method used, around 1800 and 2000 m3 ha−1 were saved with respect to the initial granted volume by the Comisión Nacional del Agua and increase in the global efficiency was also achieved (from 55% to 85%). All crop yields increased, i.e., for corn from 2.5 kg/m3 to 3.8 kg/m3. The impact of modernization accompanied with an effective operation allowed a significant increase of the crop yield and water productivity. Despite a controlled distribution of water being carried out, future research should contemplate free water demand scenarios and automation irrigation for improving the module operation