Water Level Control Structures Research Articles

Calibration of V-Notch and Compound Weirs for Subsurface Drainage Water Level Control Structures

Calibration of V-Notch and Compound Weirs for Subsurface Drainage Water Level Control Structures

The Effect of Controlled Tile Drainage on Growth and Grain Yield of Spring Barley as Detected by UAV Images, Yield Map and Soil Moisture Content

Controlled tile drainage (CTD) practices are a promising tool for improving water balance, water quality and increasing crop yield by raising shallow groundwater level and capillary rise due to drainage flow retardation. We tested the effect of CTD on growth and grain yield of spring barley, at a study site in central Bohemia using vegetation indices from unmanned aerial vehicle (UAV) imagery and Sentinel-2 satellite imagery. Tile drainage flow was slowed by fixed water level control structures that increased soil moisture in the surrounding area according to the terrain slope. Vegetation indices based on red-edge spectral bands in combination with near-infrared and red bands were selected, of which the Normalized Red Edge-Red Index (NRERI) showed the closest relationships with shoot biomass parameters (dry biomass, nitrogen concentration and uptake, nitrogen nutrition index) from point sampling at the tillering stage. The CTD sites showed significantly more biomass using NRERI compared to free tile drainage (FTD) sites. In contrast, in the period prior to the implementation of CTD practices, Sentinel-2 satellite imagery did not demonstrate higher biomass based on NRERI at CTD sites compared to FTD sites. The grain yields of spring barley as determined from the yield map also increased due to CTD (by 0.3 t/ha, i.e., by 4%). The positive impact of CTD on biomass development and grain yield of spring barley was confirmed by the increase in soil moisture at depths of 20, 40 and 60 cm compared to FTD. The largest increase in soil water content of 3.5 vol% due to CTD occurred at the depth of 40 cm, which also had a higher degree of saturation of available water capacity and the occurrence of crop water stress was delayed by 14 days compared to FTD.

Wetland Restoration Progress 39 Years After Canal Backfilling

Dredging to create canals and channels in wetlands is widespread and is a major cause of dramatically high wetland loss rates in coastal Louisiana. The dredged material placed alongside the canal forms continuous levees and can be dragged back into the canal to start wetland restoration (backfilling) but is rarely done. Thirty-three canals backfilled in the 1980s as opportunistic permit requirements were examined to determine their re-vegetation after 39 years. Sixteen of the 33 disturbed areas are now mostly restored to wetlands, and seventeen were compromised by re-dredging and other factors such as being surrounded by other canals or embedded within water level control structures. Success occurred where the natural hydrology was not artificially constrained by these structures. The re-vegetation of these 16 canals were compared to backfilled canals in the Barataria Preserve of the Jean Lafitte Historical National Park. The spoil bank was restored wetland habitat within a few years, and the open water of the canal was 70% re-vegetated after 39 years if there was no soil “plug” placed at the canal entrance during backfilling. Backfilling canals can be done on the 27 thousand abandoned canals across this coast for a low cost compared to other restoration strategies.

Long-term drainage, subirrigation, and tile spacing effects on maize production

• Not a single year in 17-yr of research received normal precipitation (Apr to Sep). • Long-term data indicated narrow tile spacing reduce yearly yield variability. • Averaged by weather classifications, yield increase upto 32 % was observed with DSI. • Yields above the DSI tiles were >60 % compared to DP & ND in dry years. • Grain yield variability generally decreased from a dry to a normal year. Flooding and drought are the most damaging abiotic stresses affecting maize production in the United States. To combat these stresses, subsurface tile drainage systems were used in conjunction with water-level control structures for subirrigation of claypan soils. The objective of this research was to develop an understanding of climate and drain tile spacing on maize plant population, grain moisture, grain yield, and grain quality measured from drainage only (DO, tile spacing 6.1 and 12.2 m), drainage and subirrigation (DSI, tile spacing 6.1 and 12.2 m), non-drained delayed planting (DP), and non-drained (ND) treatments in a 17 year (2002–2018) experiment. Production data were classified into normal, wet, and dry years based on precipitation received during the 2nd quarter (Q2, Apr. to Jun.) and 3rd quarter (Q3, Jul. to Sep.). There was not a single year in 17-yr of research that received normal precipitation in Q2 and Q3 (314 ± 43 and 288 ± 34 mm) compared to 29-yr historical precipitation data. Data were collected at 3.1 m intervals above and between the 6.1 and 12.2 m tile lines and compared among drainage treatments and weather classifications (WC). A yield increase of 20–32% (2.6 to 3.9 Mg ha −1 ) with DSI above the tile compared to DP and ND treatments when data were averaged over WC. In years classified as dry-dry, yields above the DSI tiles were >60 % compared to DP and ND. Grain yield was highest for years that had less than average precipitation during Q2 classified (dry) followed by a normal or wet Q3 period. Grain yield variability among WC was between 10.8 to 16.2 Mg ha −1 for DSI-6.1 and -12.2 above the tile whereas it was between 2.9 to 15.1 Mg ha −1 for ND. Grain yield variability generally decreased from a dry to a normal year. Long-term yield data indicated that narrower drain tile spacings with subirrigation reduce grain yield variability in dry and wet environments; however, the cost-effectiveness of these systems needs to be determined.

Use of bottom slots and submerged vanes for controlling sediment upstream of duckbill weirs

Abstract Duckbill weir is one of the water level control structures in irrigation networks, which is of interest to many engineers. Sediments transported in irrigation networks that accumulate upstream of duckbill weirs cause problems in operation, and affect the upstream water level. In this paper, submerged vanes and bottom slots are investigated for flushing the sediment downstream of the said weir. The experiments were conducted in a rectangular flume, 12 m long, and 0.6 m wide. The vanes placed in four sections were perpendicular to the sidewall. Flow-3D software was used for simulation of flow and sedimentation patterns. The results showed that submerged vanes create a secondary flow which is very useful for flushing the sediment, especially in the value of (H is head over the sidewall and P is the weir height). Further, the results showed duckbill weir efficiency (which is defined as the ratio of sediment trap to flow capacity of the weir) is as high as 47% (for values of H/P = 0.1–0.5 and total models). Finally, image processing results showed a maximum relative error of 14.4% for the simulation of the sediment pattern with Flow-3D software.

Calibration of Stainless Steel-edged V-Notch Weir Stop Logs for Water Level Control Structures

Abstract. Dependable flow rate measurements are necessary to calculate flow volumes and resulting nutrient loads from subsurface drainage systems and associated conservation practices. The objectives of this study were (1) to develop appropriate weir equations for a new stainless steel-edged 45° V-notch weir developed for AgriDrain inline water level control structures and (2) to determine if the equation was independent of flow depth in the structure. Weirs for 15 cm (6 in.) and 25 cm (10 in.) inline water level control structures were placed at three heights in each structure: at the base, 48 cm from the base, or 97 cm from the base, and the height of the nappe above the weir crest was recorded over a range of flow rates. The resulting data were fitted to equations of the form Q = aHb where Q is the flow rate, H is the height of the nappe above the weir crest, and a and b are fitted parameters. There were no significant differences in the fitted parameters across the two structure sizes or across the three weir placements. The fitted equation for these new stainless steel-edged V-notch weirs was Q = 0.011H2.28 with Q in liters per second and H in centimeters, and Q = 1.44H2.28, with Q in gallons per minute and H in inches. These equations can be used for measuring flow through AgriDrain in-line structures, although in-house weir calibration is highly recommended for specific applications, when possible. Keywords: Drainage, Flow monitoring, Subsurface drainage, V-notch weir, Weir calibration.

Fate of water and nitrate using drainage water management on tile systems in east-central Illinois

Drainage water management (DWM) is a potential edge-of-field technique that is being studied as a method to improve soil water management in agricultural fields, which may reduce nitrate losses to surface waters during the non-growing season. Inline water level control structures were installed on two adjacent tile systems draining a 34ha field located in the Upper Salt Fork of the Vermillion River Watershed in central Illinois to evaluate DWM from 2011 through 2013. The overall objective of this study was to determine the effectiveness of DWM in reducing nitrate losses from fields in a corn and soybean production system in east-central Illinois, as well as to investigate the fate of the retained water. A paired watershed approach was used to determine the impact of DWM on tile flow and nitrate load compared to a control treatment or free drainage (FD) tile system. The entire 34 ha field was under a corn (Zea mays L.) and soybean (Glycine max L.) rotation with continuous no-till. During 2011 and 2012, DWM was able to greatly reduce tile flow compared to the FD tile system. However, based on runoff and nitrate yields from the entire field, there was no measureable reduction in nitrate loss and shallow ground-water wells showed little area of influence in the field (∼2ha). Water from the DWM tile system flowed laterally to the nearby FD tile system, increasing flow and nitrate loss from the FD system. In 2013, when both tiles were under DWM, water was retained and the water table level was increased in a larger area of the field (∼6ha). However, at the end of the experiment when the control stoplogs were lowered the retained water was discharged through the tiles lines with little apparent reduction (10%) in overall water and nitrate loss for the year. Measurements of tile and well nitrate concentrations suggested that nitrate was not denitrified in the shallow groundwater of the field during the three-year study. Nitrate losses were directly proportional to tile flow each year of the study. Retrofitting DWM on an existing tile system was found to have a limited water quality benefit.

Escapement, route choice, barrier passage and entrainment of seaward migrating European eel, Anguilla anguilla, within a highly regulated lowland river

Fluvial disconnectivity can have important impacts on fish populations, including hindering movement between habitats required for different ontogenic stages. Recruitment of the European eel (Anguilla anguilla) has reduced by over 90% since the early 1980's, in part due to the effect of riverine barriers on its catadromous migration. There is a legislative requirement to restore free passage, increase habitat availability, and limit anthropogenic losses at intakes to aid eel recovery and good ecological status; necessitating an improved understanding of underlying processes. Escapement, route choice, delay at structures, and entrainment at water abstraction points of downstream migrating silver eels were examined using acoustic and Passive Integrated Transponder (PIT) telemetry in the heavily regulated lower river Stour, UK. Downstream migrating adult eel (n=69) were trapped approximately 10km upstream of the tidal limit, surgically implanted with an acoustic transducer and PIT transponder, and released between October and December in 2009 and 2010. Movements of tagged individuals were monitored by a linear array of 19 fixed acoustic receivers extending from the release site, through the last 9.2km of the freshwater catchment. Three groups of water control structures, two water abstraction intakes and several possible routes of migration are present in the reach. Seventy six and 65% of tagged eels escaped from the study reach in 2009 and 2010, respectively. Entrainment at a single intake was the principal cause of loss and positively related to rapid increases in abstraction whilst eels were in the vicinity of the intake. Route choice into the estuary was dependent on discharge over a large intertidal weir; opening regimes of a tidal gate at the termination of the alternative channel; and abstraction rate at a nearby water intake. Long delays (up to 68.5 days) and recurrent behaviour were associated with several structures in the study reach; high variability between individuals reflected the management of spill at weirs. Potential scenarios for minimising entrainment and delay through integrated management of water level control structures and abstraction rates are discussed.

Economic benefits of controlled tile drainage: Watershed Evaluation of Beneficial Management Practices, South Nation River basin, Ontario

Controlled tile drainage (CTD) is an agricultural beneficial management practice that can boost crop yields and reduce water and nutrient export from fields to surface water systems. This study examined on-farm incremental net benefits resulting from retrofitting existing tile drainage systems with inline water level control structures that control tile drainage. Corn and soybean yields (2005–2009) were respectively about 3 and 4% higher from CTD fields relative to conventionally drained fields at an experimental watershed associated with the Watershed Evaluation of Beneficial Management Practices (WEBs) program located in the South Nation river basin in eastern Ontario. The marginal cost of CTD employed in this experimental watershed was ∼Can (2006) $30 ha−1. The benefit–cost ratio was 2.6 for corn and 1.6 for soybean. A crude estimate of a payback period (without cost share) was from 3 to 4 years. Assuming all cropland in the entire South Nation river watershed where CTD is suitable, will be under CTD, the net present value of this practice is estimated to yield on farm annually about $(2006) 4 million for both crops. A crude estimate of non-user off-farm benefits of implementing CTD in this manner was ∼$0.4 million per year.

Impact of control structures on assimilative capacity of rivers and fish habitat

This research studies the impact of water level control structures on self-assimilative capacity of rivers and on fish habitat. Constructing a water level control structure in a river reach will alter its hydraulics as well as its water quality, thermal regime and fish habitat. A mathematical model is developed to simulate river hydraulics, water quality, temperature and fish habitat. Diurnal dissolved oxygen concentrations are investigated to show their impact on fish. A case of a Nile River reach was studied to investigate the impact of the existence of the Esna barrage on the water quality and fish in its upstream reach. The barrage has negative impacts on the upstream self-assimilative capacity of the rivers. The waste load that the river could absorb was only 54 % (at low flow) and 78 % (at high flow) of the entire load if no barrage was present. Including in the simulation of the effects of photosynthesis and respiration, the above mentioned percentages were raised to 54 % and 91 %, respectively. Although water level control structures have negative impacts on the upstream self-assimilative capacity of the rivers, they have positive effect on downstream dissolved oxygen concentrations due to reaeration that happens across them. Downstream dissolved oxygen concentration increased by 6 % from its upstream concentration value. The barrage has a positive effect on fish habitat in the upstream section. The weighted usable area of Tilapia fish is doubled in case of barrage existence. The barrage causes a slight decrease in water temperature that reaches an average of 0.13 degree in the month of June.

Technical Note: Calibrating Agridrain Water Level Control Structures Using Generalized Weir and Orifice Equations

Control structures have been used for drainage management in subsurface (tile) drainage. In these structures, the outlet level can be adjusted manually or electrically. To determine flow rates through these structures, we developed weir equations for manual, and an orifice equation for automated water level structures. These discharge equations were based on measured flow rates and water depths in AgriDrain structures ranging in size from 152 to 610 mm (6 to 24 in.). For each structure, a two-parameter equation for weirs with end contractions was used for low flow rates, and a one-parameter equation at higher flow rates, with the transition occurring at the point of inflection of the two-parameter equation. The fitted equations for 152-mm structures, for 203- to 610-mm structures, where Q is the flow rate (L/s), L (cm) is the width of the gate, and H (cm) is the flow depth above the gate. The discharge equation for the orifice-type opening in the structure tested was with head measured relative to the bottom of the structure, where Q is in L/s, and the units of H0 and H are cm. H is equal to H1 for unsubmerged conditions, and to the difference between H1 and the depth of submergence otherwise. This equation is consistent with the standard orifice equation if the head is measured relative to the center of the gate. These proposed equations can be used for the determination of tile flow rates where AgriDrain drainage control structures are installed, eliminating the need for additional flow measuring devices.

Modelling ditch water levels on the pevensey levels wetland, a Lowland wet grassland wetland in East Sussex, UK

The paper describes a user-friendly, physically-based model for the estimation of ditch water levels in wet grassland drainage ditches. Data requirements are standard climatic data and basic hydrological parameters, such as hydraulic conductivity. The model also requires information decribing the form and dimensions of the ditch system, as it is based on a level-volume-surface area relationship. At each time step the model calculates the level change associated with volumetric changes in storage in the system due to rainfall, evaporation, runoff, seepage and discharge through water level control structures. Application of the model to a ditch system on a National Nature Reserve on the Pevensey Levels, East Sussex provided a close replication of measured ditch water levels (R2 = 0.82). Model output data can potentially be used to provide a rapid assessment procedure to assess the impacts of different water level management strategies on ecological communities and agricultural practices in wet grassland areas.

Evaluation of Drop-Check Structures for Farm Irrigation Systems

The slope of irrigated lands varies greatly, requiring gradient control and energy-dissipating structures in most irrigation systems. Water-level control structures are also required for good water management on irrigated farms. Combination check and drop structures are often used where both types of control are needed in the same ditch. The headwall extension length and cutoff wall depth requirements for these structures vary for different soils and site conditions. Most commercial structures of a given hydraulic capacity have fixed dimensions and do not provide sufficient headwall length or cutoff wall depth for many field conditions. They also have stilling basins that are generally too narrow or too short or both. Washed-out structures and eroded ditches are a problem on many farms. A common standard design for a stable structure at a given site is a formed, cast-in-place, concrete structure. However, because of economy and convenience of installation, prefabricated structures are frequently used. Additional design and site limitation information is needed to reduce failures of prefabricated structures. Structures are needed that provide adequate erosion and water control, economy, ease of installation, and ready acceptance by the farmer. This study was made to obtain information to improve the design of drop and check structures for farm irrigation systems, and for use by the USDA Soil Conservation Service and other agencies in evaluating small structures. The study involved the evaluation and comparison of the field performance of various conventional and standard structures as they are commonly used. Several experimental structures were also included. The hydraulic and structural characteristics, together with installation and maintenance requirements, were observed. The amount of scour occurring upstream and downstream from each structure, together with bank erosion and undercutting, were observed through four seasons of operation.

Drainage Control to Diminish Nitrate Loss from Agricultural Fields

AbstractIn an attempt to reduce NO3−‐N movement to drainage waters, flashboard riser‐type water level control structures were installed in tile mains or outlet ditches at two locations to raise the water table to increase denitrification during the winter. A large reduction in NO3−‐N movement through tile lines occurred (from 25–40 to 1–7 kg/ha) in moderately well‐drained soils because of reduction in effluent volume. In the moderately well‐drained soils, there was no indication of increased denitrification in the field. In poorly drained soils, drainage control had no influence upon soil profile oxidation‐reduction potentials but resulted in approximately.a 50% reduction in NO3− movement through drainage ditches. This reduction was due to increased water movement into and through deeper soil horizons (below 1 m). The NO3−‐N concentrations and low Eh values in all profiles below 1 m indicate that the NO3− which moved to this depth underwent denitrification.