Tipping Bucket Flow Meter Research Articles

Adaptive design of tipping bucket flow meters for continuous runoff measurement

Introduction: Runoff measurement and monitoring is a laborious, time-consuming, and costly task. Additionally, common runoff monitoring usually primarily provide water level, requiring information on the stage-discharge relation. Automatic equipment such as flow meter tipping bucket (TB) is a potential option to simplify and provide continuous runoff monitoring in small catchments. However, a proper description of how to size and adapt the design under different flow conditions is still lacking.Methodology: In this paper we present a novel standardized framework for the design of TB that can be used for low-cost and real-time runoff monitoring under many different conditions. The framework consists of an estimation of the runoff peak rate using the rational equation and a volumetric capacity estimate of the cavity based on runoff rate, operation speed, and inclination angle of TB when at resting position. The proposed framework was implemented in a case study where four TBs were designed for continuous runoff monitoring from experimental plots (100 m2) with different land use (sugarcane, soybean, and bare soil).Results: During field tests (five months), the designed TBs had a recovery rate of actual runoff ranging from 61% to 81% and were able to capture features poorly studied (starting/ending time and peak flow) that have potential importance in hydrological models.Discussion: The proposed framework is flexible and can be used for different environmental conditions to provide continuous runoff data records.

Calibration and error investigation of large tipping bucket flow meters

Inherent errors in tipping bucket flow meters may limit monitoring data reliability. In this work, we perform the static and dynamic calibration of four large tipping buckets, apply different regression curves and investigate the possible measurement error sources. The volumetric capacity (static calibration) of each piece of equipment was determined. They were tested (dynamic calibration) under ten flow intensities, ranging from low to high rainfall intensities (return period larger than 100 years). For each flow rate, the measurement was recorded during six time intervals (1, 2, 5, 10, 20 and 30 min) and four regression equations - linear, potential, T vs. 1/Q and quadratic - were tested. According to the static calibration, the equipment has a volumetric capacity of 11.63 mL (TB1), 64.16 mL (TB2), 139.86 mL (TB3) and 660.95 mL (TB4). When tested under different flow rates (dynamic calibration), underestimations were identified according to the size of the cavity: TB1 (3.31%), TB2 (5.75%), TB3 (9.33%) and TB4 (13.57%). Among the alternative curves, linear regression showed the best correlation (above 99%) with the monitored data. Using this method, the measurement errors were reduced to −1.35% (TB1), 0.04% (TB2), 3.18% (TB3) and 3.73% (TB4). We investigated how the different variables (tipping speed, cavity volumetric capacity and time interval of data collection) influenced the error. Errors follow a parabolic function of tipping velocity and a linear function of cavity volumetric capacity. The time interval of data collection interfered in the data sampled, however no statistical correlation was found. Among those variables, cavity size is the most important one. Given its low cost we aimed to minimize the inherent error in large tipping buckets flow meters and encourage its application, increasing in-situ collection of hydrological data.

A generalized correction equation for large tipping-bucket flow meters for use in hydrological applications

Large tipping-bucket flow meters (TBFs, one tip > 200 ml) have been employed by hydrologists to quantify various water fluxes in a variety of contexts. The over-arching goal of this study is to develop a generalized correction equation for various TBFs. Based on our testing, we recommend the following to minimize TBF error: (1) periodic checking of the static calibration volume (c) since c is a gauge-specific value which has been found to vary after field deployment; and (2) for dynamic calibration, the use of our newly derived generalized correction equation when the tipping rate is less than 0.2 Hz. In equation form, the generalized correction equation for common TBFs with flat triangular buckets is: V = −0.75Q2 + 0.72Q + 1 (R2 = 0.843; p <0.0001), where V = v/c and v is the water volume for one tip under dynamic conditions, and Q = q/c [s−1] and q is the water flow rate into the TBF. From our field test in a Japanese cedar forest stand, using stemflow (SF) as an example, we found that use of the generalized correction equation was successful in eliminating the 2–3% error in SF amounts. Moreover, we found that the generalized correction equation performed nearly as well as gauge-specific derived correction equations. Thus, our generalized correction equation is applicable to correct flow estimates of TBFs when one does not have time and/or laboratory set-up for the laborious task of testing individual TBFs themselves. Although our correction procedure may not completely eliminate all error, we recommend use of the generalized correction equation for TBFs to improve the accuracy of water flux calculations in hydrologic studies.

Isothermal and non-isothermal infiltration and deuterium transport: a case study in a soil column from a headwater catchment

Abstract Isothermal and non-isothermal infiltration experiments with tracer breakthrough were carried out in the laboratory on one intact column (18.9 cm in diameter, 25 cm in height) of sandy loam soil. For the isothermal experiment, the temperature of the infiltrating water was 20°C to the initial temperature of the sample. For the two non-isothermal experiments water temperature was set at 8°C and 6°C, while the initial temperature of the sample was 22°C. The experiments were conducted under the same initial and boundary conditions. Pressure heads and temperatures were monitored in two depths (8.8 and 15.3 cm) inside the soil sample. Two additional temperature sensors monitored the entering and leaving temperatures of the water. Water drained freely through the perforated plate at the bottom of the sample by gravity and outflow was measured using a tipping bucket flowmeter. The permeability of the sample calculated for steady state stages of the experiment showed that the significant difference between water flow rates recorded during the two experiments could not only be justified by temperature induced changes of the water viscosity and density. The observed data points of the breakthrough curve were successfully fitted using the two-region physical non-equilibrium model. The results of the breakthrough curves showed similar asymmetric shapes under isothermal and non-isothermal conditions.

A trench study to assess transfer of pesticides in subsurface lateral flow for a soil with contrasting texture on a sloping vineyard in Beaujolais.

Subsurface lateral flow in both texture-contrast soils and catchments with shallow bedrock is suspected to be a non-point source of contamination of watercourses by pesticides used in agriculture. As a case study, the north of the Beaujolais region (eastern France) provides a favorable environment for such contamination due to its agro-pedo-climatic conditions. Environments seen in the Beaujolais region include intense viticulture, permeable and shallow soils, steep hillslopes, and storms that occur during the periods of pesticide application. Watercourse contamination by pesticides has been widely observed in this region, and offsite pesticide transport by subsurface lateral flow is suspected to be involved in diffuse and chronic presence of pesticides in surface water. In order to confirm and quantify the potential role of such processes in pesticide transfer, an automated trench system has been designed. The trench was set up on a steep farmed hillslope in a texture-contrast soil. It was equipped with a tipping bucket flow meter and an automatic sampler to monitor pesticide concentrations in lateral flow at fine resolution, by means of a flow-dependent sampling strategy. Four pesticides currently used in vine growing were studied to provide a range of mobility properties: one insecticide (chlorpyrifos-methyl) and three fungicides (spiroxamine, tebuconazole, and dimethomorph). With this system, it was possible to study pesticide concentration dynamics in the subsurface lateral flow, generated by substantial rainfall events following pesticide applications. The experimental design ascertained to be a suitable method in which to monitor subsurface lateral flow and related transfer of pesticides.

On the Estimation of Surface Runoff through a New Plot Scale Rainfall Simulator in Sardinia, Italy

Artificial rainfall is widely used to study the surface runoff process but several problems are related to the reproducibility of natural rainstorms. A new rainfall simulator and a collection system were designed and tested in the laboratory and in the field. The rainfall simulator consists of four independent lines of low-cost pressure washing nozzles operated at a pressure of 80 mbar which number and position causes the rainfall intensity delivered on the plot. The spatial rainfall distribution and his intensity were measured with 63 rainfall gauges covering the whole plot The Joss Waldvogel Disdrometer was used to characterize the rainfall produced by the rainfall simulator. The drop size distribution was obtained. The drop size spectrum ranges from 0.25mm to 3.3mm and its shape is the same to that one produced by a natural rainfall. The rainfall intensity varies from approximately 31 to 62mm/h and it is sufficiently spatially uniform (Christiansen's coefficient of uniformity is 0.62 to 0.75) over the plot. Field tests were carried out in on a grassy field with silt-loam soil in Orroli, Sardinia in July and August 2010. The values of the mean rainfall intensities obtained from field data are in accord with the laboratory values. The field site measurement includes the surface runoff, evaluated using a dedicated tipping bucket flow meter, and the soil water content measured throughout the field experiments. The results showed the good performance of this new rainfall simulator that offers the possibility to reproduce natural rainfall to gather parameters needed for hydrologic modeling. The entire designed system offers the possibility to carry out reliable measurements of the surface runoff under different rain intensities and also allows one to measure this on different temporal scales by taking into account the differen environmental conditions.

Response of rock-fissure seepage to snowmelt in Mount Taihang slope-catchment, North China

The complex physiographic and hydrogeological systems of mountain terrains facilitate intense rock-fissure seepages and multi-functional ecological interactions. As mountain eco-hydrological terrains are the common water sources of river basins across the globe, it is critical to build sufficient understanding into the hydrological processes in this unique ecosystem. This study analyzes infiltration and soil/rock-fissure seepage processes from a 65 mm snowfall/melt in November 2009 in the typical granitic gneiss slope catchment in the Taihang Mountains. The snowfall, snowmelt and melt-water processes are monitored using soil-water time-domain reflectometry (TDR) probes and tipping bucket flowmeters. The results suggest that snowmelt infiltration significantly influences soil/rock water seepage in the 0-100 cm soil depth of the slope-catchment. It is not only air temperature that influences snowmelt, but also snowmelt infiltration and rock-fissure seepage. Diurnal variations in rock-fissure seepage are in close correlation with air temperature (R(2) > 0.7). Temperature also varies with soil/rock water viscosity, which element in turn influences soil/rock water flow. Invariably, water dynamics in the study area is not only a critical water supply element for domestic, industrial and agricultural uses, but also for food security and social stability.

Functional relationships between soil water infiltration and wheeling and rainfall energy

Surface seal formation and subsoil compaction are two important factors of soil structural degradation, both of which reduce infiltration and increase surface runoff. Surface sealing has traditionally been related to rainfall energy; however, there has been very limited work on characterizing subsoil degradation resulting from wheeling energy imposed by agricultural machinery traffic. The objective of this study was to test the hypothesis that wheeling energy, either by itself or in combination with rainfall energy, would be a useful predictor of subsequent soil structural degradation. Field experiments were conducted on a heavy clay soil site in South-east Queensland, Australia which had controlled traffic and conservation tillage treatments for the previous 5 years. Soil was compacted with different axle load and wheel slips, and wheeling energy was calculated from wheel slip and rolling resistance. Simulated rain was applied at different intensities with a portable rainfall simulator. Runoff was measured with a tipping bucket flow meter, and infiltration parameters and the corresponding curve number was determined. The results showed that when soil was protected by residue cover, infiltration and runoff was governed by subsoil compaction. Under this condition, steady state infiltration rate decreased and curve number increased with increasing wheeling energy, but the constant values of steady infiltration rate (14.5 mm h −1) and curve number (93) resulted after wheeling energy exceeded 5 kJ m −2. Under non-wheeled conditions, steady state infiltration rate decreased and curve number increased linearly with increasing cumulative rainfall energy. The limited data set suggests that the degradation of soil hydraulic properties appears to be related to the sum of wheeling and rainfall energy. The data confirms that rainfall energy causes surface soil degradation, while wheeling energy caused subsoil soil degradation. Wheeling energy is relatively easy to measure or estimate, and appears to also be a useful predictor of subsoil soil degradation.

Modeling Pavement Subdrainage Systems

A comprehensive study of pavement subdrainage systems was conducted. In the study, three test sections were constructed as part of a new bypass, I-469, at Fort Wayne, Indiana. Location of the drainage layer and materials for the bituminous base course and filter materials were varied from section to section. Instrumentation was installed in the three sections during construction and included sensors to measure temperature, frost, and moisture. Tipping bucket flowmeters were attached to the subdrainage system outlet pipes. A rain gauge was located at each section. A comprehensive laboratory testing program was conducted in the study. Hydraulic conductivity tests were conducted on subgrade, filter, pavement, and trench materials. In addition to conventional saturated permeability, moisture-suction tests were conducted on all materials to determine their partially saturated permeability. Movement of water through the three pavement sections was modeled by using the finite element method analysis. Laboratory-determined hydraulic properties of each material were input directly to the analysis. Several rainfall events were analyzed. Two events were used to verify the analysis model. Subsequent analyses were conducted on new events. Data were recorded for the three sections for 3 years. Measurements indicated that one of the three subdrainage sections drained in one-third the time of the other two sections. This was in agreement with the finite element method analysis. Also, a theoretical subdrainage section was analyzed by using optimal materials from all three sections. This optimized section was shown to further reduce the time of drainage. Conclusions and recommendations address drainage layer location, filter materials, material permeability, and collector pipe capacity.

A comparative study of nitrate leaching from soils of differing textures under similar climatic and cropping conditions

This study reports a direct comparison of nitrate leaching on a field scale from a sandy soil overlying a relatively impermeable glacial till ( K sat = 30−50 mm day −1), with that from a clay loam soil overlying a similar glacial till ( K sat = 2−8 mm day −1), under nearly identical climatic and cropping conditions. Drained plots were installed at each site, and N application rate on the plots, which grew spring barley, varied from 0 to 210 kg N ha −1. Nitrate concentrations in drainage water from the two sites were measured using a simple flow-weighted sampling device and drainflow was measured using tipping bucket flow meters. Total leaching losses (including an estimate of deep percolation) in the first year of the comparison were not significantly higher on the sandy site (38 ± 11 kg N ha −1 at 150 kg N ha −1 N fertiliser application) than on the clay loam site (27 ± 4 kg N ha −1). In the subsequent 2 years, leaching losses increased at the sandy loam site. At the clay loam site leaching losses were much lower (7–11 kg N ha −1) in the final year). Timing of cultivation was an important factor influencing the amount of leaching in the clay loam soil. The effect of applied N fertiliser on nitrate leaching was small at both sites, except in the final year at the sandy site, which leached 105 kg N ha −1 at the highest fertiliser rate. The interpretation of these results was aided by concurrent chloride leaching experiments. These experiments showed that the residence time of a substantial proportion of chloride (40–50%) was longer than 1 year. This may be because of diffusion and slow convection into the glacial till horizons, where the residence time is long.

Hydraulic requirements of geocomposite fin-drain materials utilized in pavement subdrainage

A study was conducted to determine the hydraulic requirements of geocomposite fin-drain materials utilized in pavement subdrainage. The study consists of a laboratory testing program, field subdrainage outflow studies, and analysis of all data to define the fin-drain core flow capacity requirements. Two separate laboratory testing procedures were used to evaluate the hydraulic properties of five selected geocomposite fin-drain materials. One test procedure followed the general guidelines of ASTM D4716-87. The second test procedure followed a non-standard approach which utilized a 7·3 m long channel. Field subdrainage outflow data were obtained from two test sites in Illinois. These data are presented in terms of volume of outflow as a function of time. The data were collected by use of tipping-bucket flow meters. A comparison was made between the observed core flow capacity of the fin-drain materials in the laboratory and the flow volume observed from field subdrainage systems. Based on this comparison it was indicated that geocomposite fin-drain systems will be required to provide flow-zone capacities in excess of 567·8 litres/h at 0% pavement gradient and in excess of 757 litres/h at gradients of 1% or greater, to compare with a standard pipe and sand envelope system. When compared with a more permeable aggregate envelope system or a high-performance fin-drain system, flow-zone capacities in excess of 757 litres/h to 1135·5 litres/h may be desirable, depending upon the pavement gradients and the number and size of joint and crack openings. In-plane flow rates based on ASTM D4716-87 should be greater than 3·3–3·7 litres/s/m width for 61-cm-long specimens tested at a hydraulic gradient of 0·1 and unit load similar to field conditions. Based on faulting measurements it is indicated that a fin-drain subdrainage system can improve pavement performance to a level equivalent to or better than that for some standard systems.

A tipping bucket flowmeter for roadside gully runoff

AbstractA tipping bucket flowmeter designed for the measurement of inflows to roadside gully pots is described. It is braced within the pot above the liquor and the runoff is fed to it via a glass fibre funnel and a hose. Whilst it can be calibrated to only 0·71 s−1, it is very effective at low flows and has a number of advantages over the well known Institute of Hydrology Gully Meter. Its use at Redbourn, Hertfordshire for roads on highly permeable soils shows that for both rainfall and artificial irrigation the ‘losses’ are very large and highly variable even within a single housing estate road.

THE SEASONAL VARIATION OF SOIL EROSION BY WATER IN SOUTHWESTERN QUEBEC

Fallow plots were maintained at four sites that varied with respect to soil type and slope aspect and gradient to determine seasonal patterns of soil loss in southwestern Quebec. Equipment used to measure and record runoff included tipping-bucket flowmeters and Datapod digital recorders. Soil loss was measured on a seasonal basis from September 1983 to August 1985, to compare the percentage of annual soil loss by water that occurred during winter and summer months. Summer soil loss accounted for approximately 80% of the total annual soil loss from coarse-textured sites. Winter soil losses at the fine-textured site were responsible for almost 90% of the annual soil loss from that site. Key words: Soil erosion, universal soil loss equation, spring runoff

A LOW-COST TIPPING BUCKET FLOWMETER FOR OVERLAND FLOW AND SUBSURFACE STORMFLOW STUDIES

Details on the design, construction, calibration, performance and application of a low-cost tipping bucket flowmeter are given. The flowmeter consists of two balanced water-receiving units, which tip back and forth as they are alternately filled by water. With each tip, an electrical pulse is generated by activating a microswitch and the pulse is recorded by an event recorder. The flow rate is computed from the number of pulses recorded. Over the range of 1.4–13.6 liters/min the tipping bucket read approximately 3% lower than a calibrated rotameter. A sampling funnel can be installed in conjunction with the flowmeter to collect water samples for chemical analysis.