History of Drainage in the Bureau of Reclamation

In the early days of the Reclamation Service, the criteria for irrigability of lands generally consisted of two elements: (1) is water available? and (2) can we get the water to the land? Within a few years, many of the early projects were experiencing reduced agricultural productivity and reduced ability to repay construction loans because the soils were becoming waterlogged and saline. By 1915, construction of subsurface drainage facilities had been initiated on several projects. However, at the time, subsurface drainage was more of an art than a science. Much of the world’s experience with agricultural drainage had been gained in humid areas which were quite different from arid areas. With no standards and limited knowledge of ground water movement, these early drainage efforts met with varying degrees of success. This paper summarizes the development of scientific methods to ensure successful application of drainage in a sustainable irrigated agriculture. Reclamation has introduced these methods to solve irrigated drainage problems at the international level. This paper will address the international experience, and how the same design and construction methods and procedures are now being used to design corrective drainage facilities for dams and other major structures and to support environmental enhancement programs.     

History and Evaluation of Hargreaves Evapotranspiration Equation

A brief history of development of the 1985 Hargreaves equation and its comparison to evapotranspiration (ET) predicted by the Food and Agricultural Organization of the United Nations (FAO) Penman-Monteith method are described to provide background and information helpful in selecting an appropriate reference ET equation under various data situations. Early efforts in irrigation water requirement computations in California and other arid and semiarid regions required the development of simplified ET equations for use with limited weather data. Several initial efforts were directed towards improving the usefulness of pan evaporation for estimating irrigation water requirements. Similarity with climates of other countries allowed developments in California to be extended overseas. Criticism of empirical methods by H. L. Penman and others encouraged the search for a robust and practical method that was based on readily available climatic data for computing potential evapotranspiration or reference crop evapotranspiration (ETo). One of these efforts ultimately culminated in the 1985 Hargreaves ETo method. The 1985 Hargreaves ETo method requires only measured temperature data, is simple, and appears to be less impacted than Penman-type methods when data are collected from arid or semiarid, nonirrigated sites. For irrigated sites, the Hargreaves 1985 ETo method produces values for periods of five or more days that compare favorably with those of the FAO Penman-Monteith and California Irrigation Management Information Services (CIMIS) Penman methods. The Hargreaves ETo predicted 0.97 of lysimeter measured ETo at Kimberly, Idaho after adjustment of lysimeter data for differences in surface conductance from the FAO Penman-Monteith definition. Monthly ETo by the 1985 Hargreaves equation compares closely with ETo calculated using a simplified, “reduced-set” Penman-Monteith that requires air temperature data only.     

Reduced-Runoff Irrigation of Sudan Grass Hay, Imperial Valley, California

Sudan grass is a moderately salt-tolerant annual that is capable of substantial osmotic adjustment under high soil salinity conditions, but little is documented about its actual water use and yield under saline conditions. We estimate water use and evaluate the effects of “reduced-runoff” irrigation on soil salinity associated with Sudan grass hay production during a three-year field study (1996–98) in the Imperial Valley, California. The reduced-runoff irrigation method relies on the application of a simplified volume-balance surface irrigation model, and can result in negligible surface runoff; however, its use may have adverse impacts on soil salinity. Despite an anticipated salinity-induced yield reduction of about 15% associated with an average soil salinity of 6 dS∕m (0–0.6 m depth), use of the reduced-runoff method resulted in satisfactory crop yields, practically no tailwater runoff, and a slight decrease from the initial average profile soil salinity. The average applied water depth and estimated consumptive use (ETc) during the project were 1,019 and 935 mm, respectively, resulting in an average hay yield of 14.4 Mg∕ha versus the 1996–98 county average of 12.6 Mg∕ha. The project average ETc/ET0 and yield∕ETc ratios of 0.73 and 15.5 kg∕ha?mm, respectively, were approximately 15% less than those estimated from water-use-efficiency studies, probably as a result of salinity-induced hay yield reduction.     

Noise Reduction Methods for Weighing Lysimeters

Mechanical vibration of the grass and crop weighing lysimeters, located at the University of California West Side Field Research and Extension Station at Five Points, Calif. generated noise in lysimeter mass measurements and reduced the quality of evapotranspiration (ET) data. The estimated power spectral density (PSD) for grass lysimeter mass data acquired at 1.3?ms intervals contained a large peak at 11?Hz. Crop lysimeter data produced similar peaks at frequencies greater than 1?Hz. An effective method for eliminating this noise source is arithmetic averaging of the data, which should be acquired sufficiently rapidly to avoid aliasing. The PSD also increased with decreasing frequency in the range 1.0–0.1?Hz. This noise was addressed by Savitsky–Golay (SG) filtering using 7-, 11-, and 15-point filters. Each filter was applied to the same data set consisting of 2,560 measurements taken during a 1-min interval every 10?min over a 26.3-h period. Noise reduction factors, defined as the ratio of standard deviation of filtered lysimeter mass to standard deviation of unfiltered mean values of lysimeter mass for subsequences of the same data, were 0.90, 0.88, and 0.86 for the 7-, 11-, and 15-point filters, respectively. For the daytime data only, the factors were 0.88, 0.85, and 0.83. The SG filters were more effective during daytime when most of the lysimeter ET occurs. These methods are simple enough to be programmed into commercially available dataloggers for real time filtering. Hourly averages of the standard deviations of lysimeter mass measurements bear a distinct nonlinear relationship to hourly mean wind speed confirming earlier suppositions that wind loading causes noise in counterbalanced weighing lysimeters.     

Parametric Study of Unsaturated Drainage Layers in a Capillary Barrier

Unsaturated drainage layers (UDLs) have been demonstrated to greatly increase the lateral diversion capacity of capillary barriers. The inclusion of a UDL allows native soils suitable for vegetation growth to be used as the finer soil as lateral drainage properties of the layer no longer need to be considered. A comprehensive numerical study was conducted to investigate the influence of the interface slope and the UDL material on the system's ability to laterally divert downward moving moisture. A capillary barrier system with and without a UDL was simulated for 10 years using daily varying climatic data for three locations in the United States. Three different sands were simulated as the UDL and were modeled at slopes of 5, 10, and 20%. The numerical results confirm that the inclusion of an unsaturated drainage layer at the fine∕coarse interface of a capillary barrier can provide significant improvements in the performance of the cover system by laterally draining water. This improvement in performance may allow the system to be successfully implemented in climates wetter than previously were thought suitable. The diversion length (the distance water is diverted laterally with no downward flow through the fine∕coarse interface) of a capillary barrier with a UDL was found to be proportional to the slope of the fine∕coarse interface. In addition, a relationship between lateral diversion lengths in a capillary barrier and the UDL material was developed and found to be dependent on the unsaturated flow characteristics of the UDL. These relationships allow the performance of a variety capillary barrier UDL designs to be calculated knowing the behavior of one system for a given location.     

Field Performance of a Compacted Clay Landfill Final Cover at a Humid Site

A study was conducted in southern Georgia, USA, to evaluate how the hydraulic properties of the compacted clay barrier layer in a final landfill cover changed over a 4-year service life. The cover was part of a test section constructed in a large drainage lysimeter that allowed continuous monitoring of the water balance. Patterns in the drainage (i.e., flow from the bottom of the cover) record suggest that preferential flow paths developed in the clay barrier soon after construction, apparently in response to desiccation cracking. After four years, the clay barrier was excavated and examined for changes in soil structure and hydraulic conductivity. Tests were conducted in situ with a sealed double-ring infiltrometer and two-stage borehole permeameters and in the laboratory on hand-carved blocks taken during construction and after four years of service. The in situ and laboratory tests indicated that the hydraulic conductivity increased approximately three orders of magnitude (from ≈ 10?7?to? ≈ 10?4?cm?s?1) during the service life. A dye tracer test and soil structure analysis showed that extensive cracking and root development occurred throughout the entire depth of the barrier layer. Laboratory tests on undisturbed specimens of the clay barrier indicated that the hydraulic conductivity of damaged clay barriers can be underestimated significantly if small specimens (e.g., tube samples) are used for hydraulic conductivity assessment. The findings also indicate that clay barriers must be protected from desiccation and root intrusion if they are expected to function as intended, even at sites in warm, humid locations.     

Effects of Electroosmosis on Natural Soil: Field Test

A unique configuration of horizontal sheet-like electrodes was used in the field at a site in Ohio that was underlain by silty clay glacial drift to induce electroosmotic flow and to characterize the effects of electroosmosis on soil properties (e.g., electrical conductivity and pH). The lower electrode was created at a depth of 2.2 m by filling a flat-lying hydraulic fracture with granular graphite, and the upper one was a metallic mesh placed at a depth of 0.4 m and covered with sand. The electrodes were attached to a DC power supply, creating an electrical gradient of 20–31 V∕m and a current of 42–57 A within approximately 20 m3 of soil. Total energy applied was 5,500 kW?h during approximate 4 months of operation. Electroosmotic flow rates of 0.6–0.8 L∕h were observed during tests lasting several weeks, although total flow rate (electroosmotic plus hydraulic) was strongly influenced by fluctuations of the ground-water table. The ratio of applied current to voltage decreased from 0.9 to 0.6 A∕V and was mainly due to a decrease in electrical conductivity of the soil. A low pH front developed at the anode and migrated toward the cathode. The velocity of the pH front per unit voltage gradient was 0.014 (cm∕day)/(V∕m). This was 40 times slower than what has been reported from laboratory experiments using kaolinite as a medium. These results confirm the feasibility of using horizontal electrodes at shallow depths, but they also underscore some important differences between the geochemical effects observed during field tests in natural soils and those seen in laboratory tests using ideal materials.     

Design and Management of Subsurface Horizontal Drainage to Reduce Salt Loads

Many irrigated areas have shallow water tables creating waterlogging and salinization problems. This has often been controlled by installation of subsurface horizontal pipe drainage; however, these systems export large amounts of salt off farm in the drainage effluent. Improved design and management of subsurface drainage systems to reduce drainage salt loads were tested in a replicated field experiment. Deep, widely spaced drains allowed to flow without control were compared to drains with management to reduce drain flow. These were also compared with shallow, closely spaced drains that protected the root zone only and an undrained control. The deep drains flowed continuously during the two irrigation seasons with an electrical conductivity of around 11 dS∕m resulting in a drainage salt load of 5,867 kg∕ha. The management measures reduced drainage volume and salinity resulting in a 50% reduction in salt load. The shallow drains only flowed directly after an irrigation or rainfall event with low salinity, around 2 dS∕m, resulting in a 95% reduction in salt load. This showed that by management there is great potential for reducing salt mobilization in existing drainage systems, and for new systems shallower drains will minimize salt loads.     

Investigation of Factors Affecting Vertical Drain Behavior

Some influencing factors on vertical drain behavior were investigated by laboratory tests as well as by back-analyses of test embankments on vertical drain improved subsoil at Saga Airport, Saga, Japan. Based on the results from this study, suggestions are made on determining the design parameters for vertical drain improvement. For the discharge capacity test of a prefabricated vertical drain, confining the drain in clay is essential. Also, due to the creep of the filter and the clogging caused by the fine particles entering the drainage channel, the long-term discharge capacity is significantly smaller than the short-term one, and this should be considered in design. For smear effect, a new equation is proposed for determining the ratio of the hydraulic conductivity of the natural subsoil to that of the smear zone, which considers the fact that laboratory tests normally underestimate the hydraulic conductivity of natural deposits. Regarding the effect of the sand mat, the numerical analysis results in this study show that if the hydraulic conductivity of sand is larger than 10?4 m∕s, the assumption of a free drainage condition in the sand mat may not result in significant error. Finally, a methodology of predicting the behavior of vertical drain improved subsoil is proposed.     

Case Study of a Full-Scale Evapotranspiration Cover

The design, construction, and performance analyses of a 6.1?ha evapotranspiration (ET) landfill cover at the semiarid U.S. Army Fort Carson site, near Colorado Springs, Colo. are presented. Initial water-balance model simulations, using literature reported soil hydraulic data, aided selection of borrow-source soil type(s) that resulted in predictions of negligible annual drainage ( ? 1?mm/year). Final construction design was based on refined water-balance simulations using laboratory determined soil hydraulic values from borrow area natural soil horizons that were described with USDA soil classification methods. Cover design components included a 122?cm thick clay loam (USDA), compaction ? 80% of the standard Proctor maximum dry density (dry bulk density ～ 1.3?Mg/m3), erosion control measures, top soil amended with biosolids, and seeding with native grasses. Favorable hydrologic performance for a 5?year period was documented by lysimeter-measured and Richards’-based calculations of annual drainage that were all <0.4?mm/year. Water potential data suggest that ET removed water that infiltrated the cover and contributed to a persistent driving force for upward flow and removal of water from below the base of the cover.     

Sustainable Root Zone Salinity and Shallow Water Table in the Context of Land Retirement

This study uses five years of field data from the Land Retirement Demonstration Project located in western Fresno County of California to develop a comprehensive theoretical and numerical modeling framework to evaluate the specific site conditions required for a sustainable land retirement outcome based on natural drainage. Using field data, principles of mass balance in a control volume, the HYDRUS-1D software package for simulating one-dimensional movement of water, heat, and multiple solutes in variably-saturated media, and a model-independent parameter optimizer, the processes of soil water and solute movement in root zone and deep vadose zone were investigated. The optimization of unsaturated soil hydraulic parameters and downward flux (natural drainage) from the control volume against observed vadose zone salinity levels and shallow groundwater levels yield difficult to obtain natural drainage rate as a function of water table height within the control volume. The results show that the unsaturated soil hydraulic properties and the downward flux from the soil profile are the critical parameters. A “natural drainage approach” to sustainable land management for drainage-impaired land is proposed. With this approach it is feasible to design a sustainable land use regimen for drainage-impaired lands in general and retired lands in particular.     

Sediment-Laden Flow in Open-Channels under Noncapacity and Capacity Conditions

To determine the suspended load component of sediment transport in open-channel flow, the vertical distribution of the concentration of suspended particles is of importance. It is usual to determine this distribution by solving the diffusion-convection equation under appropriate boundary conditions. The exponent in the resulting equation is the Rouse number, defined as z′ = vss/βu*. The -value has been the subject of much research. In natural alluvial channels the sediment-laden flow is usually in capacity (saturation) condition, implying that the flow will charge (saturate) itself with particles available in the bed load and∕or on the bed itself. However, simulation of sediment-laden flow in a laboratory flume is achieved typically by externally adding particles to the flow. Consequently, it is not certain that the flow was in capacity condition. The resulting -values are often values for noncapacity conditions. They should not be used for natural alluvial channels, because they are misleading. Reported herein are experiments performed in the laboratory under noncapacity, as well as under capacity, conditions. This study focuses on the experimental determination of the -value, which incorporates the ratio of the sediment flux and the momentum flux , as well as the velocity and concentration profiles, ?ū∕?y and ?/?y, respectively. For experiments with small particles, d50 = 0.135 mm, the -values at capacity condition are smaller than unity; at noncapacity condition, the -values are usually larger than the ones at capacity condition, but all are still smaller than unity.     

Determining Primary Productivity of Lake Roosevelt with 14C

During two sampling trips in 1997, primary productivity was measured at 11 stations in Lake Roosevelt using a radioactive carbon tracer capable of determining subtle changes in water quality. Both spatial and temporal variations in productivity were observed. For the August 1997 field trip, productivities on the mainstem reservoir ranged from 485 to 1,243 mgC∕m2∕d, with an average value of 783 mgC∕m2∕d. Temporal differences between the August and October trips varied by as much as 880 mgC∕m2∕d. The data are compared to measurements taken over a four-year period to determine subtle, long-term changes in the water quality. Productivity at Lake Roosevelt is heavily influenced by tributary inflow, and generally increased in the reservoir reaches below the mouths of the tributaries. Mainstem sites between the tributaries had lower productivities than the upstream and downstream tributary sites, indicating that nutrients may be rapidly utilized in the immediate vicinity of the inflows. However, productivities in the tributary arms were consistently low, despite the fact that their physicochemical properties stimulated growth in the reservoir. The productivity data illustrate the difficulty in characterizing a large water body as a homogeneous quantity in terms of assessing loading impacts. The results also demonstrate that long-term changes in water quality can be masked by short-term events. The long-term trend is that Lake Roosevelt, a eutrophic/mesotrophic lake, is becoming an oligotrophic lake, but seasonal rainfall events influence the lake's specific characterization.     

Nonlinear Analysis of Laterally LoadedRock-Socketed Shafts

In this paper, a nonlinear continuum method is developed to predict the load-displacement response of drilled shafts under lateral loading. The method can consider drilled shafts in a continuum consisting of a soil layer overlying a rock mass layer. The deformation modulus of the soil is assumed to vary linearly with depth, and the deformation modulus of the rock mass is assumed to vary linearly with depth and then to stay constant below the shaft tip. The effect of soil and∕or rock mass yielding on the behavior of shafts is considered by assuming that the soil and∕or rock mass behaves linearly elastically at small strain levels and yields when the soil and∕or rock mass reaction force p (force∕length) exceeds the ultimate resistance pult (force∕length). For the calculation of the ultimate resistance pult of the soil, methods that are available in the literature are used. To calculate the ultimate resistance pult of the rock mass, a method based on the Hoek-Brown strength criterion is proposed. The proposed method is verified by comparing its results with available elastic solutions and field test data, and it is finally applied in the design of a bridge foundation in Massachusetts.     

Economics of Furrow Irrigation under Partial Infiltration Information

The effects of partial infiltration and furrow geometry information on furrow irrigation design and economic return to water were quantified on a single furrow (reference furrow) and field-wide (10-furrow set) basis using a kinematic-wave furrow irrigation model in conjunction with an economic optimization model. A furrow sampled at 10 locations was assumed to represent the actual field condition. Subsamples were randomly drawn from the 10 samples and return to water was maximized. These suboptimal designs were applied to the actual furrows and monetary loss due to lack of information was simulated. The monetary loss was less for furrow irrigation designs having high inflow rates ($0.38∕furrow, $17∕ha) than for the low inflow rates ($2.27∕furrow, $100∕ha). Average loss decreased from $31∕ha ($0.71∕furrow) to $0∕ha in the case of the reference furrow, and from $1.0∕furrow ($44∕ha) to $0.3∕furrow ($13∕ha) in the case of the 10-furrow set for the samples sizes of 1 and 10, respectively.     

Simulation of Vertical Transport in Mining Pit Lake

Subaqueous disposal is a technique that can, under suitable circumstances, delay or mitigate the release of material containing high levels of dissolved compounds, for example, acid rock drainage, into the surrounding environment. The technique places the material in question under a relatively inert cap of lighter fluid in a deep basin, such as that left after mining. In many situations, because of low diffusion rates, the material may be considered as being isolated from the environment. However, there are a number of naturally occurring physical mechanisms that can quite efficiently bring this material to the surface, and hence, to the surrounding environment. We describe a modeling application to a deep and steep-sided chemically stratified lake using an extended version of the lake and reservoir water quality model, DYRESM, incorporating algorithms for detailed ice cover, heat fluxes, and also internal wave-driven boundary mixing. Sheltering and shading of the meteorological forcing is taken into account in the model. Both the field data and the model confirm the capping effects of the freshwater cap (S < 0.7 g∕L) overlying the relatively salty water (S > 0.85 g∕L) in the pit. Examination of the mechanistically determined vertical eddy diffusivities suggest that at depths below the surface mixed layer, double diffusion dominates over vertical mixing due to bottom-generated turbulence stemming from basin-scale internal waves. The ability of the model to simulate for periods longer than about 6 months is not addressed in this study.     

Comparison of Priestley-Taylor and FAO-56 Penman-Monteith for Daily Reference Evapotranspiration Estimation in Georgia

The climate in Georgia and other southeastern states of the United States is considered to be humid and the annual precipitation is usually greater than the annual potential evapotranspiration (ET). However, during several months of the year, supplemental irrigation is needed to prevent yield reducing water stress due to the temporal rainfall variability and sometimes due to long-term droughts. The Priestley-Taylor (PT) equation has been used operationally in Georgia to compute ET for irrigation scheduling because of its simplicity, its general acceptable performance in humid regions, and its limited input requirements. A recent study for a site in the humid southeastern United States found that PT overestimated ET and was less accurate than the FAO-56 Penman-Monteith (PM) among some of the approaches that were evaluated. The objective of this study was to assess the potential improvement that can be achieved by replacing PT with FAO-56 PM in Georgia and other southeastern states in a humid climate. More than 70 weather stations across Georgia are available as part of the Georgia Automated Environmental Monitoring Network. Nine representative sites, including Blairsville in a mountainous area and Savannah in a coastal area, were selected to assess the potential improvements that may be achieved by replacing PT with FAO-56 PM. Each site had at least 10 years of daily records that included minimum and maximum air temperature, solar radiation, wind speed, and vapor pressure deficit. PT underestimated the daily and monthly ET during the winter months in the central and southwestern areas and overestimated the daily and monthly ET during the summer months in the coastal and mountainous areas. For the warm season, i.e., April through September, PT slightly overestimated the cumulative ET in the central and southwestern areas, moderately for the mountainous area and severely for the coastal area. Based on these results, it is anticipated that the use of FAO-56 PM for estimating ET will standardize the ET calculations and improve irrigation efficiency in Georgia, especially for the mountainous and coastal areas.     

Utility of Column Lysimeter for Design of Soil Aquifer Treatment System for Wastewater Renovation Using Artificial Neural Networks

An artificial neural network (ANN) model is developed to study the correlation of data with reference to various wastewater pollution parameters (biochemical oxygen demand, chemical oxygen demand, suspended solids, NH4, PO4) using two scales of experiments viz. column lysimeter and a pilot soil aquifer treatment (SAT) system for wastewater renovation in India. A unique feature of the study is that the primary treated wastewater was directly applied to SAT system for renovation in contrast to the secondary treated effluent used in most of the other studies that have been reported. The analysis of data using ANN as a tool indicates that the column lysimeter data are useful for design of SAT systems and it is possible to predict the effluent quality for SAT system based on the inputs from lysimeter experiments. The study highlights the utility of column lysimeter studies for evolving design parameters for a full-scale SAT system thereby obviating the need for pilot SAT studies which are site specific, time consuming, and expensive. Thus, the study suggests that the experimental data from lysimeter studies at a particular site can be used to predict performance of field-scale SAT systems without going in for actual experimentation. Further, the field data from one site could be utilized for design of SAT systems at other locations provided the climatic and hydrogeological conditions viz. soil matrix characteristics and wastewater characteristics, etc., are similar.     

Water Table Management to Improve Drainage Water Quality in Semiarid Climatic Conditions of Iran

A lysimeter study was conducted in the field in Karaj, Iran to investigate the effects of water table management on water quality of subsurface drainage effluents. Drain volumes, nitrate-N concentration, phosphorus concentration, and electrical conductivity of drain effluents were monitored during the growing seasons of alfalfa (Medicago scutellata). Totally 12 lysimeters consisted of four treatments were used in this study, of which nine of them were equipped with subirrigation (SI) and the other three with free drainage (FD) systems. Annual alfalfa (Medicago scutellata) was planted in all lysimeters. Water table levels were kept at 30 cm (SI30), 50 cm (SI50), and 70 cm (SI70) below the soil surface in SI-lysimeters and more than 100 cm below the soil surface in FD-lysimeters. The results of this 2-year study showed a significant reduction in nitrate-N concentrations in SI-lysimeters compared to FD-lysimeters. In 2005, the mean nitrate-N concentrations in drainage effluent were reduced by 84% in the SI30 and by 82% in the SI50, relative to FD. Similarly, in 2006, drain water depth and nitrate-N concentrations were significantly reduced relative to FD. The forage dry matter production from SI30 and SI50 were significantly higher than those from FD in both years. In 2006, the average of dry matter production was increased by 69 and 89% by the SI30 and SI50, respectively, relative to FD. The average electrical conductivity of drainage water was reduced in SI lysimeters compared to FD lysimeters that meet Iranian standard level (3 dS/m). There are no statistically significant differences in phosphorous concentration in drainage water of different treatments. Finally, the results of this 2-year study indicate that the water table management practices are economically and environmentally feasible in Iran in order to have a sustainable agriculture.