Deep Percolation Water Research Articles

Padrões de amostragem e intensidade de krigagem na caracterização do armazenamento de água no solo, em área irrigada por pivô central

A qualidade da irrigação tem sido descrita por parâmetros calculados admitindo-se ser a capacidade de armazenamento de água no solo uma constante. No entanto, tal propriedade do solo apresenta-se variável no espaço. A preocupação com aspectos ambientais e econômicos tem levado ao conceito de manejo da cultura em áreas específicas, o que torna importante o conhecimento da distribuição espacial de propriedades do solo. A geoestatística torna possível a identificação da estrutura de dependência espacial e o mapeamento de uma propriedade do solo. O objetivo deste trabalho foi identificar intensidades de amostragem e de krigagem em blocos, adequadas para estimar o armazenamento de água no solo, para desejado nível de precisão nos parâmetros que caracterizam a qualidade da irrigação. Em área irrigada por pivô central, no campus da ESALQ/USP, foi feita uma amostragem segundo uma transeção radial com espaçamento de 2,83 m. Em cada ponto, foi determinada a capacidade de armazenamento de água no solo, entre as tensões de 0,01 e 0,08 MPa, para 0,30 m de profundidade. De posse do semivariograma obtido para os dados da transeção, foi feita a krigagem em blocos de diferentes comprimentos, entre 2 e 30 m, para espaçamentos amostrais simulados de malhas com lado entre 2 e 20 m, na direção da transeção. A cada combinação de espaçamento e comprimento de bloco, foram associados a respectiva variância de krigagem e o volume de água percolado, calculados com base em lâmina aplicada igual à média dos valores de armazenamento medidos. A krigagem deve ser realizada com os menores valores de lado de bloco (2 m), desde que recursos computacionais não sejam limitantes. O uso de amostragem intensa não promoveu ganho significativo de qualidade das estimativas, em relação aos maiores espaçamentos. Malha de lado igual a 20 m pode ser usada, embora o desejável seja lado de 10 m. É necessária uma amostragem na curta escala para a identificação do semivariograma nas distâncias inferiores a estas. Apesar de promover uma suavização, a krigagem deve ser usada na descrição do padrão espacial de armazenamento, por permitir melhor avaliação dos volumes de excesso e de déficit e, principalmente, por permitir identificar os locais onde eles ocorrem.

Soil Water Dynamics after Alfalfa as Influenced by Crop Termination Technique

AbstractBecause of their deep roots and high water demand, alfalfa (Medicago sativa L.) hay crops can reduce water available to crops following in the rotation. Recharging the soil water profile after alfalfa is, therefore, a high priority in dryland cropping systems. The objective of this study was to investigate effects of alfalfa crop termination date (late June, early August, and in spring immediately before spring wheat seeding) and method (herbicides, tillage, and herbicides plus tillage) on soil water conservation, and establishment, yield, and water use efficiency (WUE) of a following spring wheat (Triticum aestivum L.) crop. Experiments were conducted over 5 site‐years in a subhumid region of western Canada. Herbicide termination resulted in greater total water recharge and a faster rate of water recharge than treatments involving tillage. Greater efficiency of soil water recharge for herbicide termination after the first hay harvest (late June) appeared to cause deep water percolation at one site. Delaying termination until after the second hay harvest (early August) did not reduce soil water availability at spring seeding of the following wheat crop, but increased reliance on overwinter soil water recharge. Delaying herbicide treatment until spring reduced water at seeding and wheat yields in some cases. Compared with treatments involving tillage, herbicide treatments resulted in higher levels of groundcover (i.e., greater soil erosion control), higher WUE, and higher grain yields. Herbicide termination after the second hay harvest produced the most favorable overall outcome; better than the traditional approach of tillage after the first hay harvest.

The effect of permafrost on stream biogeochemistry: A case study of two streams in the Alaskan (U.S.A.) taiga

Understanding interactions between permanently frozen soils and stream chemistry is important in predicting the effects of management, natural disturbance and changing perma- frost distribution on stream ecosystems and nutrient budgets in subarctic watersheds. Chemical measurements of groundwater, soil water and stream water were made in two watersheds in the taiga of interior Alaska. One watershed (HiP) had extensive permafrost and the other (LoP) had limited permafrost. Soil water collected within the rooting zone (0.3-0.5 m) in both watersheds was high in dissolved organic carbon (DOC), dissolved organic nitrogen (DON) and dissolved inorganic nitrogen (DIN) but low in dissolved minerals (dominantly Ca, Mg and Na) and conductivity. The reverse was true for groundwater from springs and wells. Permafrost in the HiP basin prevented deep percolation of water and generated stormflows rich in DOC. The presence of permafrost in HiP resulted in higher fluxes of DOC, DON and DIN into stream water from upland soils.

Nitrogen Movement with Furrow Irrigation Method and Fertilizer Band Placement

AbstractAlternate‐furrow irrigation has been proposed as a method to increase irrigation water use efficiency, increase capture and storage of rainfall during the irrigation season, and decrease deep percolation of water. We hypothesized that less fertilizer leaching would occur if the applied fertilizer were spatially separated from the irrigation water in a furrow irrigation system. A study was conducted on a Fort Collins loam (fine‐loamy, mixed, superactive, mesic Aridic Haplustalf) in 1994 and 1995 near Fort Collins, CO. Nitrogen uptake by corn (Zea mays L.) and N leaching were determined with alternate‐furrow and every‐furrow irrigation water applications, each with fertilizer bands of 15N‐enriched (NH4)2SO4 placed either in the row or in the furrow. In 1994 fertilizer N leached to ≈1 m for the every‐furrow irrigation with fertilizer placed in the irrigated furrow, but to 0.5 m or less for the other treatments. In 1995 the fertilizer leaching was similar among the treatments because of less irrigation and more rainfall during the growing season. There were no statistically significant differences for irrigation water placement effects on plant biomass or total N uptake, indicating that alternate‐furrow irrigation is not detrimental to crop production compared with every‐furrow irrigation for similar applications of water. This study showed that placing fertilizer in the nonirrigated furrow of an alternate‐furrow irrigation system or placing fertilizer in the row with either alternate‐ or every‐furrow irrigation has the potential to decrease fertilizer leaching without reducing crop productivity.

Water Rights to Return Flow from Urban Landscape Irrigation

This paper presents our research on the issue of water rights to return flow from irrigation of urban landscapes. Municipalities in Colorado’s Front Range, with rights to transmountain water and other “use to extinction” water rights, have begun to examine lawn irrigation as a possible source to augment their supplies. They claim that a significant percentage of water applied to lawns is not used by the turf grass, and eventually returns to the streams and ground-water systems. In accordance with their water rights, this deep percolation water can be reused by the municipalities. This paper reviews the methodologies used by various cities to estimate deep percolation and return flow as a function of applied water. It then analyzes how these findings were evaluated by the Water Courts in their decisions concerning credits for return flow. To provide an independent analysis of the irrigation–return flow relationships, research was recently conducted at the Colorado State University (CSU) (1992–96). The CSU research results indicate that the small lysimeters used by various cities are of acceptable accuracy compared to a large lysimeter and standard evapotranspiration equations for estimating consumptive use. For estimating deep percolation, results of this research support the findings of the previous studies conducted for the city of Colorado Spring and for the Cottonwood Water and Sanitation District in Denver.

Corn Growth and Nitrogen Uptake with Furrow Irrigation and Fertilizer Bands

AbstractFurrow irrigation is commonly used to provide supplemental water to row crops. Alternate‐furrow irrigation has been proposed as a method to decrease deep percolation water losses as well as the leaching of fertilizer and pesticides. A study was conducted on a Ulm clay loam (fine, smectitic, mesic Ustic Haplargids) in 1994 and 1995 near Fort Collins, CO. Corn (Zea mays L.) growth and N uptake were measured under alternate‐furrow and every‐furrow irrigation water applications, each with fertilizer bands placed either in the row or in the furrow. Nitrogen‐15‐depleted (NH4)2SO4 fertilizer was used to distinguish plant uptake of fertilizer N from uptake of naturally occurring N. There were no differences in plant response to alternate‐furrow or every‐furrow irrigation water placement for the same amount of water applied. Greater fertilizer‐N uptake occurred with row placement than with furrow placement of N fertilizer. Early in the growing season, fertilizer‐N uptake from row placement was from 2 to 10 times the fertilizer‐N uptake from furrow placement. By the end of the growing season, the average total‐N uptake from row placement was 12% greater than for furrow placement. Placing the fertilizer in the nonirrigated furrow of the alternate‐furrow irrigation treatment decreased N availability by 20% compared with the average of the other treatments. If alternate‐furrow irrigation is used to increase water use efficiency in furrow‐irrigated fields, placing the N fertilizer in the nonirrigated furrow of the alternate‐furrow irrigation system could decrease N availability because of drier soil conditions in the nonirrigated furrow. Row placement of N fertilizer seems to be beneficial in both alternate‐furrow and every‐furrow irrigation applications.

Growth and yield responses of almond (Prunus amygdalus) to trickle irrigation

Growth and yield responses of developing almond trees (Prunus amygdalus, Ruby cultivar) to a range of trickle irrigation amounts were determined in 1985 through 1987 (the fifth through seventh year after planting) at the University of California's West Side Field Station in the semi-arid San Joaquin Valley. The treatments consisted of six levels of irrigation, ranging from 50 through 175% of the estimated crop evapotranspiration (ETc), applied to a clean-cultivated orchard using a line source trickle irrigation system with 6 emitters per tree. ETc was estimated as grass reference evapotranspiration (ET0) times a crop coefficient with adjustments based upon shaded area of trees and period during the growing season. Differential irrigation experiments prior to 1984 on the trees used in this study significantly influenced the initial trunk cross-section area and canopy size in the 50% ETc treatment and 125% ETc treatment. In these cases, treatment effects must be identified as relative effects rather than absolute. The soil of the experimental field was a Panoche clay loam (nonacid, thermic, Typic Torriorthents). The mean increase in trunk cross-sectional area for the 3-year period was a positive linear function (r 2 = 0.98) of total amounts of applied water. With increases in water application above the 50% ETc treatment, nut retention with respect to flower and fertile nut counts after flowering, was increased approximately 10%. In 1985 and 1987, the nut meat yields and mean kernel weights increased significantly with increasing water application from 50% to 150% ETc. Particularly in the higher water application treatments, crop consumptive use was difficult to quantify due to uncertainty in estimates of deep percolation and soil water uptake. Maintenance of leaf water potentials higher than −2.3 MPa during early nut development (March through May) and greater than −2.5 MPa the remainder of the irrigation season (through August) were positively correlated with sustained higher vegetative growth rates and higher nut yields.

Economic and environmental impacts of water quality protection policies: 1. Framework for regional analysis

Agricultural production systems provide some unique challenges for assessing the regional impacts of water quality protection policies. A modeling framework is proposed for assessing the environmental and economic consequences of groundwater quality protection policies at the regional level. The model consists of three components: (1) a crop simulation/chemical transport model, (2) a regional economic optimization model, and (3) an aquifer groundwater flow model. The three submodels are linked and run recursively to simulate producer response to alternative water quality policies over a multiple‐year time horizon. Model solutions provide projections of production practices employed on various resource situations across the region. Economic evaluation of alternative policies may be based upon regional agricultural income, crop production levels, input use, and changes in aquifer water levels over time. Measures of agricultural nonpoint source pollution provided by the model include nitrate, phosphorus and pesticide loadings in deep percolation and runoff water, as well as sediment losses.

Reduction of Deep Percolation and Drain Water

Principle considerations in examining water‐management options for the control of toxic trace elements in agricultural drainage waters are addressed, including a number of improvements in off‐farm water delivery systems, as well as efficiency of on‐farm irrigation systems and water reuse. Potentials exist to improve off‐farm water‐delivery systems through reductions in seepage losses with canal linings, operational spills through systems irrigation scheduling, and interception of water losses and reuse. Potentials also exist in improving on‐farm water management through improved irrigation application systems, on‐farm irrigation scheduling, and other cultural products such as changes in cropping patterns. These on‐farm management options will affect net farm income due to increased costs of equipment and structures, increased labor requirements, and changes in crop revenue. But not all of these will have a negative economic input. For instance, efficient irrigation systems not only value drainage but tend to increase crop yield or decrease crop production inputs. Installation of structural system improvements and use of system scheduling of water delivery may result in decrease in operation and maintenance costs. Institutional and legal constraints, particularly water‐right ownership, may constrain efforts to minimize drain‐water production and toxic‐element problems. The long‐term economic viability of irrigated agriculture will require careful consideration of both off‐farm and on‐farm management options.

Drainage of Clay Overlying Artesian Aquifer. I: Hydrologic Assessment

The performance of subsurface drains in a clay soil overlying an artesian aquifer is evaluated at a site in Imperial Valley, California. Field studies are undertaken to examine water and salt movement through the soil profile and the response of subsurface drains under surface irrigation. Water penetrated to all depths soon after the passing of the irrigation advance front. Peak drain flow occurred shortly after irrigation had stopped. Soil and drain‐water salinity remain nearly constant throughout the year, and have changed little over the past several decades. The drains intercept only a small percentage of deep percolation water and do not contribute significantly to the overall drainage of the field.

Elemental and Geochemical Analysis of the Umm-Khurisan Spring Water (Al-Hasa Area, Eastern Province, Saudi Arabia)

Abstract The Umm-Khurisan spring is a small spring, located in the Al-Hasa area in the Eastern Province of Saudi Arabia. The high concentrations of total hardness, total disolved solids, Cl−, NO− 3 and F−, and the high value of the electrical conductivity of the spring water are above the limits recommended by the World Health Organization standards with regard to potability. Concentrations, of other minor constituents are around these limits. Therefore, it is recommended that the Umm-Khurisan spring water should not be used for drinking purposes. The Umm-Kurisan water is a saline water with medium sodium hazard. Such water should be used only on soils of moderate to good permeability. The Umm-Kurisan spring water probably is of meteoric origin of deep percolating water.

Irrigation management for groundwater quality protection

Deep percolation flow below agricultural and can transport nitrate and pesticide residues to underlying groundwater. Irrigated agriculture in dry climates can also contaminate groundwater with salt from irrigation water and with trace elements such as selenium leached from the vadose zone. Groundwater contamination by agricultural chemicals can be minimized by using best management practices (BMPs) for crop production (including low-input sustainable agriculture or other source control) and for irrigation. Irrigation systems should be designed and managed for zero or minimum deep percolation during the growing seasons to keep fertilizer and pesticides in the root zone as long as possible. At other times, irrigation efficiencies can be lower to produce enough deep percolation water for leaching salts out of the root zone. Because of spatial variability and preferential flow, however, some deep percolation and movement of chemicals may still occur, even if the irrigation efficiency is 100%. BMPs should be developed to minimize such deep percolation flow.

Effect of Irrigated Agriculture on Groundwater

The time it takes for deep percolation water from irrigated fields to reach underlying groundwater increases with decreasing particle size of the vadose zone material and increasing depth to groundwater. For average deep percolation rates, decades may be required before the water joins the groundwater. Due to nonuniform irrigation applications and preferential flow, some deep percolation water will reach the groundwater much faster. Dissolved salts, nitrate, and pesticides are the chemicals in deep percolation water of main concern in groundwater pollution. Movement of pesticides may be retarded in the vadose zone, but biodegradation may also be slowed due to reduced organic carbon content and microbial activity at greater depths. Because of the large area of irrigated land in the world and the real potential for groundwater pollution, more research is necessary on downward movement of water and chemicals in the vadose zone.

Evaluation of Irrigation‐Nitrogen Management Practices for Celery using Continuous‐Variable Irrigation

AbstractThe interaction between N source and irrigation rate and the resultant effects on NO‐3 leaching were characterized for celery, using a modified line‐source sprinkler system which applied water across fertilizer plots at rates varying from replacement of evapotranspiration (ET) to 1.8 ET. Nitrogen, as (NH4)2SO4 (AS), was applied at a rate of 300 kg/ha in split applications (AS300); sulfur‐coated urea (SCU) was applied alone at 300 kg N/ha (SCU300), all preplant, or in a combination with 150 kg N/ha SCU preplant and 150 kg N/ha AS sidedressed (SCU150AS150). Plants with the AS300 and SCU300 treatments removed significantly less N at the lowest irrigation rate than those with the SCU150AS150 treatment, but this difference was not observed at high irrigation rates. All three N treatments produced large accumulations of NO‐3 beneath the root zone which increased with increased leaching. Yields from the fertilized treatments were significantly higher at all irrigation levels than yields from unfertilized plots, but were not different from each other. Yields also did not vary substantially across the range of irrigation rates, indicating that deep percolation of water and NO‐3 can be minimized through improved irrigation management without reducing celery yield.

Controlled Degradation and/or Protection Zones — Nonsensea

ABSTRACTMan's activities are an ever‐increasing threat to ground‐water quality. New EPA policies encourage cities to discharge sewage effluent on land. Irrigated agriculture is incompatible with high‐quality ground water where deep percolation water is not removed by drainage. Present drinking‐water quality standards cannot be used to determine the suitability of water for potable use if such water is waste‐water‐derived. Where sewage effluent is applied to land, persistent trace organics occur in underlying ground water. Some of these organics may be carcinogenic or otherwise toxic, and much additional research is needed. Controlled degradation of ground water still is degradation. High‐quality ground‐water resources either are to be protected, or aquifers eventually must be abandoned as sources of high‐quality drinking water. In the long term, there is no in‐between. The choice will be dictated by economic and environmental considerations. For example, the most economical use of aquifers below irrigated valleys ultimately may be to serve as facilities for treatment, storage, and conveyance of municipal waste water from surrounding communities, so that this water can be used again for unrestricted irrigation. While such uses of aquifers may be far off, they should be anticipated now to allow proper planning.

Deep Percolation in a Furrow-Irrigated Sandy Soil

ABSTRACT IRRIGATING sandy soils with shallow water tables creates a potential for deep percolation losses of water and nitrogen and consequently, nitrate pollution of ground-water. The amount and nitrate con-tent of percolate was measured with eight vacuum extractors buried be-low the root zone in a sandy, furrow-irrigated cornfield. Total irrigation-season percolation was 17.6 cm, which was 25 percent of the water leaving the root zone. The maximum percolation rate was over 0.37 cm/day when the corn root system was not yet fully developed and when heavy rainfall followed irrigating. More frequent irrigations with smaller amounts of water should reduce percolation. Percolation of nitrate-nitrogen was 2.5 kg/ha/cm of percolate when N (67 kg/ha) was applied in solution in the irrigation water and 3.0 kg/ha/cm of percolate when anhy-drous ammonia N (90 kg/ha) was sidedressed. Percolation of nitrate-nitrogen was affected more by total deep percolation of water than by the method of fertilizer application.