Agricultural Drainage Systems Research Articles

Effectiveness of Constructed Wetlands in Reducing Nitrogen and Phosphorus Export from Agricultural Tile Drainage

AbstractMuch of the nonpoint N and P entering surface waters of the Midwest is from agriculture. We determined if constructed wetlands could be used to reduce nonpoint N and P exports from agricultural tile drainage systems to surface waters. Three treatment wetlands (0.3 to 0.8 ha in surface area, 1200 to 5400 m3 in volume) that intercepted subsurface tile drainage water were constructed in 1994 on Colo soils (fine‐silty, mixed, superactive, mesic Cumulic Endoaquoll) between upland maize (Zea mays L.) and soybean [Glycine max (L.) Merr.] cropland and the adjacent Embarras River. Water (tile flow, precipitation, evapotranspiration, outlet flow, and seepage) and nutrient (N and P) budgets were determined from 1 Oct. 1994 through 30 Sept. 1997 for each wetland. Wetlands received 4639 kg total N during the 3‐yr period (96% as NO3‐N) and removed 1697 kg N, or 37% of inputs. Wetlands decreased NO3−N concentrations in inlet water (annual outlet volume weighted average concentrations of 4.6 to 14.5 mg N L−1) by 28% compared with the outlets. When the wetlands were coupled with the 15.3‐m buffer strip between the wetlands and the river, an additional 9% of the tile NO3−N was apparently removed, increasing the N removal efficiency to 46%. Overall, total P removal was only 2% during the 3‐yr period, with highly variable results in each wetland and year. Treatment wetlands can be an effective tool in reducing agricultural N loading to surface water and for attaining drinking water standards in the Midwest.

An integrated drainage network analysis system for agricultural drainage management. Part 1: the system

This is the first of two papers that elaborate an integrated drainage network analysis system (IDNAS) for agricultural drainage management. In this paper, the system components, functions and implementation are presented. The IDNAS comprises an agricultural drainage network module, an evapotranspiration (ET) module and an event-based spatio-temporal module. The network module is designed to model a typical agricultural drainage system and to perform the specific tasks for network assessment, monitoring and simulation in a geographical information system (GIS). The ET module is used to estimate real-time evapotranspiration from remotely sensed imagery and to update the water balance model. The spatio-temporal module comprises a computer watertable simulation model and routines providing linkage between event data and GIS thematic layer for event-based analysis. Specialized data processing routines have been developed to link the network data model with temporal hydrological modeling to allow computation of important network parameters such as flow travel time, discharge and capacity, and to dynamically simulate drainage response to individual rainfall events. A common interface has been developed to link those components, and to interact with the users. The Arc/Info GIS was used for the system implementation. With those components and functions, the system is well suited for assessment and management of agricultural drainage systems. In the second paper, case studies are presented which show how the system can be used for efficient agricultural drainage management, such as drainage capacity assessment, discharge computation, and event-based acid drainage evaluation and management.

Monitoring Wadi El Raiyan Lakes of the Egyptian Desert for Inorganic Pollutants by Ion-Selective Electrodes, Ion Chromatography, and Inductively Coupled Plasma Spectroscopy

Wadi El Raiyan is a great depression located southwest of Cairo in the western desert of Egypt, one of the most arid regions of the world. In 1973, Wadi El Raiyan was connected with the agricultural wastewater drainage system of the El Faiyum province to provide a reservoir for the wastewater that exceeded the capacity of Lake Qarun north of the province. Pollutants from agricultural waste including pesticides and fertilizers as well as other effluents of industrial activities and runoffs certainly will pass into the biotic elements of the ecosystem. This report presents the status of inorganic pollutants including anions, cations, and trace metals in the two lakes and the surrounding springs of Wadi El Raiyan using ion chromatography, ion-selective electrodes, and inductively coupled plasma emission spectroscopy. The report also includes the levels of selected metals in the vegetation community of the area. The result of this investigation revealed a great improvement in water quality of the Wadi El Raiyan lakes compared to 1988 report by Saleh et al. Mercury was not detected in any of the samples and the level of lead was significantly reduced. Cadmium levels were much higher than those seen earlier. The higher level of cadmium might be used as an indicator to track the contamination of water by human waste. Concentrations of common anions were not significantly different from those reported earlier. However, an increase in the level of cyanide was observed. Levels of heavy metals in vegetation around the lakes were also found to be lower than previously reported.

CONTINUOUS MEASUREMENT OF DRAINAGE DISCHARGE

The west side of the San Joaquin Valley of California has had drainage disposal problems since irrigation wasintroduced in the early 1900s. Selenium toxicity problems associated with the Kesterson Reservoir caused closure of theexisting agricultural drainage system in 16 194 Ha (40,000 acres) in 1986. The continuing need for drainage of irrigatedagricultural lands has prompted several water management studies by the Water Management Research Laboratory of theUSDA. One of the essential data requirements in these studies is the quantification of drain flows. A measurement stationwas constructed for this purpose employing a manhole with a 90 V-notch weir and datalogging electronics to providehourly water flow data. Power was supplied by solar and conventional sources. Construction details, costs (for a solar-poweredstation), and resulting data are shown. As configured, the measurement station has provided seasonal datastreams for analysis during three years of operation.

Environmental impacts of deep opencast limestone mines in Laegerdorf, Northern Germany

Deep opencast mines for limestone of Upper Cretaceous age in the northernmost state of Germany, Sch!eswig-Holstein, greatly impact the local environment. In three pits with depths of nearly 100 m, mine pumping affects deeper aquifers and sometimes shallow ones as well. The total amount of mine water pumped ranges up to 6*106 m3/year. Due to the relief of hydraulic pressure, saline water is ascending from deeper parts of the limestone and infiltrating into the pits via the minefloor. The salt content of the deep ground water exceeds that of the sea in some places. The saline water causes process engineering problems and adversely affects the water quality of a receiving channel. Shallow aquifers are affected by dewatering due to hydraulic connections to the limestone. In places with organic soils (mostly peat of Holocene age), this is followed by ground subsidence, which damages buildings and agricultural drainage systems.

Fate of Seasonal, Terrestrial Nutrient Inputs to a Shallow Seagrass Dominated Embayment

A highly seasonal input of water-borne nutrients flows into Geographe Bay from a network of agricultural drainage systems, from July to September (winter) when the drains flow. Near-shore nutrient concentrations increased from 15 to 150μgl−1for total phosphorus and from 200 to 2000μgl−1for total nitrogen. However, greater than 100m offshore, these nutrients were no longer detectable.The yearly input from terrestrial sources (255 tonnes of nitrogen) accounts for two-thirds of the nitrogen required to produce maximum biomass of the seagrassPosidonia sinuosa. Other sources of nutrients are likely to be important in maintaining seagrass biomass and productivity. These sources include seagrass wrack decomposition, sediment nutrient release and groundwater inflow to the embayment. Nitrogen appeared to be the limiting nutrient for seagrass growth in Geographe Bay in summer when nutrients were not in excess.

Selenium Biotransformations by a Euryhaline Microalga Isolated from a Saline Evaporation Pond

Selenium ecotoxicology is one of the best known examples of environmental impact resulting from toxic element biotransformations and food chain transfers. Despite this, it is becoming recognized that Se biotransformations by microbes and plants may also be a key to in situ bioremediation of Se contamination in large-scale cases such as agricultural drainage systems. We have isolated an euryhaline alga (Chlorella sp.) from Se-laden drainage pond waters and utilized GC−MS and multi-nuclear NMR to characterize its aerobic biotransformation activity for Se oxyanions. We found that this alga was active in volatilization of alkylselenides, production of putative selenonium precursor(s) of alkylselenides, and precipitation of Se, while exhibiting very low accumulation of the toxic selenomethionine in free form. Thus, such euryhaline microalgae are potentially important for in situ Se bioremediation and Se biogeochemical cycling in contaminated saline habitats.

The Relationships among Man's Activities in Watersheds and Estuaries: A Model of Runoff Effects on Patterns of Estuarine Community Metabolism

Activities of man in rivers and their watersheds have altered enormously the timing, magnitude, and nature of inputs of materials to estuaries. Despite an awareness of large-scale, long-term changes in river-estuarine watersheds, we do not fully understand the consequences to estuarine ecosystems of these activities. Deforestation, urbanization, and agriculturalization have changed the timing and nature of material inputs to estuaries. Conversion of land from forest to almost any other land use promotes overland flow of storm runoff; increases the timing, rate and magnitude of runoff; and increases sediment, organic matter, and inorganic nutrient export. It has been estimated that total organic carbon levels in rivers have increased by a factor of 3–5 over natural levels. Man’s activities have also changed the magnitude of particulate organic carbon relative to dissolved organic carbon export and the lability of the organic matter. Historically, rivers and streams had different features than they do today. Two of man’s activities that have had pronounced effects on the timing and quality of river water are channelization and damming. Agricultural drainage systems, channelized and deepened streams, and leveeing and prevention of overbank flooding have had the combined effect of increasing the amplitude and rate of storm runoff, increasing sediment load, increasing nutrient delivery downstream, and decreasing riparian wetland productivity. Dams on the other hand have altered natural discharge patterns and altered the downstream transfer of sediments, organic matter, and nutrients. Patterns of estuarine community metabolism are sensitive to variations, in the timing, magnitude, and quality of material inputs from watersheds. The autotrophic-heterotrophic nature of an estuary is determined by three primary factors: the ratio of inorganic to organic matter inputs, water residence time, and the overall lability of allochthonous organic matter inputs. A simulation model is used to explore the effects of man’s activities in watersheds on the spatial patterns of production and respiration in a generalized estuarine system. Examined are the effects of variations in the ratios of inorganic and organic nitrogen loading, the residence time of water in the estuary, the degradability of allochthonous organic matter, and the ratio of dissolved to particulate organic matter inputs. Simulations suggest that the autotrophic-heterotrophic balance in estuaries is more sensitive to variations in organic matter loading than inorganic nutrient loading. Water residence time and flocculation-sedimentation of organic matter are two physical factors that most effect simulated spatial patterns of metabolism in estuaries.

Sensitivity of agricultural drainage systems to changes in climatic inputs

Drainage design and the performance of existing pipe systems is examined in the light of anthropogenetically induced climate change. It is shown that changes in UK drainage design could be influenced more by structural changes in agricultural production systems demanding higher standards of performance than by small shifts in rainfall totals. Although existing drainage systems might not meet their design criteria, any short-fall will be relatively minor for small increases in design rate. A hydraulic model is used to predict the performance of existing pipe drainage systems in the light of increasingly intense rainfalls. It is shown that existing systems could be stressed hydraulically, increasing the possibility of drainage failure, potential generation of surface runoff, and attendant risk of mole drain collapse.

In situ bacterial selenate reduction in the agricultural drainage systems of western Nevada

Dissimilatory in situ selenate reduction to elemental selenium in sediments from irrigated agricultural drainage regions of western Nevada was measured at ambient Se oxyanion concentrations. Selenate reduction was rapid, with turnover rate constants ranging from 0.04 to 1.8 h-1 at total Se concentrations in pore water of 13 to 455 nM. Estimates of removal rates of selenium oxyanions were 14.38, and 155 mumol m-2 day-1 for South Lead Lake, Massie Slough, and Hunter Drain, respectively.

Irrigation water pricing policies to reduce and finance subsurface drainage disposal

Disposal of water collected in agricultural subsurface drainage systems has normally been done without direct charge to the farmer. In some cases, drainage water disposal costs are becoming very high so that the institution of incentives for the farmer to reduce drainage volumes and pay for their safe disposal are appropriate. The consequences of various irrigation water pricing policies on optimal irrigation application, profits and drainage volumes were analyzed for cotton grown under three levels of irrigation uniformity. The unregulated case led to applied water and drainage flows that exceeded the economically efficient levels. A direct charge on drainage waters equal to their disposal costs induced economically efficient water application but required a drainage water volume monitoring system. A flat fee on irrigation water could be set to induce an economically efficient water application; but in this case, the revenues generated by the imposition of the extra charge greatly exceeded the costs of disposal. Selection of the flat fee to equalize revenues and treatment costs resulted in excessive irrigation compared to the economically efficient levels. Tiered water pricing, whereby the unit water price is increased as volume increases, is another option. When the seasonal crop evapotranspiration was selected as the level to impose the tiered pricing, the tiered price could be selected to induce economically efficient applications. However, the revenues generated by the tiered price were less than the costs for disposal. Water pricing policies suffer from being sensitive to irrigation uniformity. Investment in irrigation technology to improve irrigation uniformity is justified, and the level of investment increases as the costs for drainage water disposal increase.

Processes affecting the distribution of selenium in shallow groundwater of agricultural areas, western San Joaquin Valley, California

A study was undertaken to evaluate the processes affecting the chemistry of shallow groundwater associated with agricultural drainage systems in the western San Joaquin Valley, California. The study was prompted by a need for an understanding of selenium mobility in areas having high selenium concentrations in shallow groundwater. Groundwater samples were collected along transects in three artificially drained fields where the age of the drainage system varied (15, 6, and 1.5 years). Selenium concentrations in the drain water also varied (430, 58, and 3700 μg/L, respectively). Isotopic enrichment and chemical composition of the groundwater samples indicate that saline‐ and selenium‐enriched water has evolved as a result of evaporation or transpiration of groundwater. This evaporated, isotopically enriched water is being displaced by more recent, less saline irrigation water percolating through the root zone. This displacement seems to be a process whereby sodium chloride and sodium sulfate water is being replaced by more dilute calcium sulfate and calcium bicarbonate water.

Comment on Oneota Ridged Field Agriculture in Southwestern Wisconsin

Existing evidence to support the interpretation that Oneota garden beds in southwestern Wisconsin functioned as wetland agricultural drainage systems is reviewed. In addition, previously unreported analyses of sediments from the Sand Lake Site (47 Lc44), La Crosse County, Wisconsin, are presented. Based on these data the interpretation that the Sand Lake Site garden beds represent wetlands drainage systems is rejected.

Incorporating Uncertainties into the Design of Agricultural Subsurface Drainage Systems

A new approach to linking uncertainties due to climate and soil properties is described for the design of agricultural subsurface drainage systems. The climatic uncertainty is incorporated by using a first-order finite-state Markov chain model. The uncertainty in soil properties is considered by the first and second order analyses of uncertainty.The methods are briefly explained and an example is given that shows how by linking uncertainties the proposed method can be used to develop individualized designs, taking into account the amount of risk a particular farmer is willing to accept in his farming enterprise.

Prediction of nitrogen and phosphorus losses as related to agricultural drainage system design

The purpose of this study was to determine the effects of differing degrees of improved agricultural drainage on the long-term efflux of N and P from poorly drained soils common to the North Carolina Coastal Plain. The effect of using controlled drainage on efflux was also investigated. Computer simulations were used to predict the losses from 6 soils for a 20-year period. The simulations indicate that both drainage system design and management can have significant effects upon N and P efflux in drainage water. Drainage systems designed to give good subsurface drainage lost 17–35 kg ha −1 year −1 more NO 3-N than systems with poor subsurface drainage. Good subsurface drainage decreased total P lost by 0.2-0.4 kg ha −1 year −1 on the mineral soils studied. The increase in N lost because of installing a good subsurface drainage system can partially be offset by utilizing controlled drainage. Under the conditions simulated in this study, controlled drainage reduced the nitrate efflux by as much as 34%, but the reduction varies with soil and management conditions. Controlled drainage does, however, result in a small increase in P efflux under the conditions simulated.

Will Drainage Increase Spring Soil Temperatures in Cool and Humid Climates?

ABSTRACT IT is generally assumed that installing agricultural drainage systems will increase the soil temperature faster in spring. Historically this information is based on an experiment where a wet muck soil heats up slower than a dry mineral soil. A theoretical examination for non-seepage areas found the soil type and not the degree of wetness to be responsible for temperature differences.

Avoiding failure of leachate collection systems

Examples of failures of leachate collection systems have been surveyed by telephone throughout the U.S.A. and evaluated in terms of literature and other personal contacts. Failures in hazardous waste landfills are seldom reported but are expected to be similar to failures in other landfills and agricultural drainage systems. Major failures related to inadequate design, construction and operation are discussed together with suggestions for reducing the incidence of failures.

Avoiding Failure of Leachate Collection Systems

Examples of failures of leachate collection systems have been surveyed by telephone throughout the U.S.A. and evaluated in terms of literature and other personal contacts. Failures in hazardous waste landfills are seldom reported but are expected to be similar to failures in other landfills and agricultural drainage systems. Major failures related to inadequate design, construction and operation are discussed together with suggestions for reducing the incidence of failures.

A Probabilistic Approach to Agricultural Drainage Design

ABSTRACT A new approach to the assessment of a proposed agricultural drainage system is presented. The method makes use of the concept of a Markov chain and presents results in the form of a probability of obtaining a satisfactory workable period during the critical planting period with any proposed drain depth and spacing.

INTERPRETATION OF SOIL DRAINAGE GROUPS FROM SOIL TAXONOMY—SOUTHERN ONTARIO

Ontario Soil Survey data for 278 soil series were interpreted to describe relationships between soil characteristics and the movement of water in saturated zones of the soil profile. Based on family particle size classes, groups of soil families, similar in profile and parent material, were formed. Groups were ordered in terms of increasing ability of soil to transmit water, as interpreted by Soil Conservation Service guidelines. The ordered groups were separated into two parts using the European concepts for surface water gley and groundwater gley soils. Six groups of surface water gley soils were differentiated in which surface water was interpreted as the principle source of saturation. Groundwater was interpreted to be the principle source of saturation for three groups of groundwater gley soils. Principles applied to grouping and ordering were augmented by data for soil texture and structure to develop a generalized profile description for each group. The generalized profile description was translated into a five symbol code by which the interpretation is applied to individual soil series within a group. The code is intended to enhance application of soil survey data to design of buried agricultural drainage systems. Key words: Soil physical characteristics, drainage characteristics, hydrologic soil groups, surface water Gleysols, groundwater Gleysols, pseudogleysols