SURFACE WATER QUALITY IMPACTS OF TILLAGE PRACTICES UNDER LIQUID SWINE MANIJRE APPLICATION1

ABSTRACT: Field studies were conducted to investigate the effects of tillage practices on the saturated hydraulic conductivity, and quantity and quality of surface runoff water resulting from the application of the liquid swine manure as a fertilizer. As part of the study, infiltration experiments were conducted on silt-loam soil with no-tillage (NT) and disk tillage (DT) practices. Liquid swine manure was applied on test plots, and the rainfall was applied by the portable rainfall simulator. The infiltration data was analyzed for the saturated hydraulic conductivity (K8) and runoff volume determinations. The surface runoff water was analyzed for total N, total P, ammonia, and nitrate concentration determinations. The study indicated that the tillage had significant effects on K_s, and quantity and quality of runoff water. The K_s values of the NT plots were found to vary from 0.693 to 1.734 mm/min, with a mean of 1.494 mm/min, while they varied from 1.056 to 2.543 mm/min, with a mean of 2231 mm/mm in the DT plots. The total N, total P, ammonium nitrogen and nitrate nitrogen concentrations were lower in runoff generated from DT plots, compared to that from the NT plots. The chemical concentration levels were significantly different in runoff waters collected one-day after manure application than in those collected 40-days after the manure application. Study suggested that the DT practice must be preferred over the NT practice if liquid swine manure is used as the fertilizer. The study is further continued to assess the long-term impacts of swine manure application and tillage on the quantity and quality of surface runoff water.     

USING CURVE NUMBERS TO DETERMINE BASELINE VALUES OF GREEN-AMPT EFFECTIVE HYDRAULIC CONDUCTIVITIES1

ABSTRACT: Since the trend in infiltration modeling is currently toward process-based approaches such as the Green-Ampt equation, more emphasis is being placed on methods of determining appropriate parameters for this approach. The SCS curve number method is an accepted and commonly used empirical approach for estimating surface runoff, and is based on numerous data from a variety of sources. The time and expense of calibrating process-based infiltration parameters to measured data are often prohibitive. This study uses curve number predictions of runoff to develop equations to estimate the “baseline” hydraulic conductivities (K_b) for use in the Green-Ampt equation. Curve number predictions of runoff were made for 43 soils. K_b values in the Water Erosion Prediction Project (WEPP) model were then calibrated so that the annual runoff predicted by WEPP was equal to the curve number predictions. These calibrated values were used to derive an equation that estimated K_b based on the percent sand, percent clay, and cation exchange capacity of the soil. Estimated values of K_b from this equation compared favorably with measured values and values calibrated to measured natural runoff plot data. WEPP predictions of runoff using both optimized and estimated values of K_b were compared to curve number predictions of runoff and the measured values. The WEPP predictions using the optimized values of K_b were the best in terms of both average error and model efficiency. WEPP predictions using estimated values of K_b were shown to be superior to predictions obtained from the curve number method. The runoff predictions all tended to be biased high for small events and low for larger events when compared to the measured data. Confidence intervals for runoff predictions on both an annual and event basis were also developed for the WEPP model.     

A CASE STUDY OF SHALLOW FLOW PATHS IN A STEEP ZERO-ORDER BASIN1

ABSTRACT: Soil water potentials, slope throughflow, runoff chemistry, and isotopic composition were monitored in a 97 m² zero-order basin within the Maimai 8 watershed on the South Island of New Zealand, for a natural rain storm and two artificial water applications. Contrary to results previously reported for other portions of the Maimai catchment, much of the runoff occurred as a shallow subsurface organic layer flow. For the 47 mm natural rain event, pre-storm soil matric potential ranged from ?60 to ?150 cm H₂O. No saturation was produced within the profile, and the majority of storm runoff emanated from flow within the organic horizon perched on the mineral soil surface. Hillslope applications corroborated this interpretation by showing >90 percent new water flushing with negligible mineral soil moisture response. Although the mechanisms cited in the text are not representative of the entire catchment, the study demonstrates: (1) the value of a combined physical-chemical-isotopic approach in quantifying slope processes, and (2) the heterogeneous nature and diversity of slope runoff pathways in a relatively homogeneous catchment.     

CHANGES TO INFILTRATION AND INTERRILL EROSION FROM LONG-TERM PRESCRIBED BURNING IN LOUISIANA1

ABSTRACT: Effects of long-term prescribed burning on infiltration and interrill erosion were assessed on two longleaf pine-bluestem sites in Louisiana. Treatments represented biennially-applied winter, spring, or summer burning on an upland sandy loam site for 20 years; and annual winter or spring, and biennial winter or spring burns on a bottomland silt loam site for 10 years, with unburned controls. Immediate effects of burning were a reduction in surface cover, exposing soil to raindrop impact. Burning the sandy loam site increased interrill erosion after winter and spring treatments, but produced no immediate changes in infiltration capacity or time to runoff irrespective of treatment season. Rapid recovery of under-story vegetation mitigated soil exposure. Biennial burning did not increase interrill erosion, or reduce infiltration capacity and time to runoff on the sandy loam site after 20 years. A complete herbaceous understory covered the silt loam site two years after treatment. Interrill erosion was not significantly increased, or infiltration capacity and time to runoff decreased on burning treatments than unburned controls on the silt loam site. Litter biomass was important in predicting interrill erosion. No surface cover condition could be linked to variability in infiltration capacity. This study provides evidence for the resiliency of a longleaf pine-bluestem association to prescribed burning.     

APPLICATION OF SCS INFILTRATION MODEL1

ABSTRACT: The SCS infiltration model was applied to the Ralston Creek watershed in eastern Iowa. The criteria to determine the various model parameters were revised to obtain a better agreement between the observed and computed total runoffs. A procedure to calibrate the infiltration model is presented. The infiltration model was used in conjunction with an overland flow model to develop flood hydrographs. The results indicate that SCS infiltration model adequately describe the distribution of losses.     

A DIGITAL OVERLAY TECHNIQUE FOR EVALUATION OF POTENTIAL INFILTRATION AND RECHARGE1

ABSTRACT: A common problem encountered during regional planning and development of ground water dependent communities is the difficulty in deciding which areas should be preserved for aquifer recharge purposes. This paper describes the development and application of a digital overlay technique for objective evaluation and ranking of potential infiltration and potential recharge areas. Equations are developed which relate the hydrologic parameters pertaining to infiltration and recharge in a surface aquifer-confined aquifer system. These equations make use of discrete data, yet by application in a digital overlay technique results are obtained in the form of spatial distributions in order for regional trends and conditions to be examined. An application of this procedure to the 551,000 acre region of central Florida, known as the Green Swamp, is discussed. The results are presented in the form of computer generated maps which identify and rank areas of potential recharge to the aquifer system.     

CAPACITY EXPANSION PLANNING MODEL FOR WASTE WATER TREATMENT AND I/I CONTROL1

ABSTRACT: A dynamic programming model is presented for planning the optimal capacity expansion sequence of waste water treatment plants servicing sewerage systems with infiltration/inflow. The model employs a nonlinear deterministic demand function for waste water treatment plant capacity. Model output provides the optimal timing, size, and sequence for treatment plant capacity expansion projects and infiltration/inflow removal projects. An example problem is presented and solved.     

INFLUENCE OF VEGETATION,ROCK COVER,AND TRAMPLING ON INFILTRATION RATES AND SEDIMENT PRODUCTION1

ABSTRACT: This study evaluated the impact of selected soil surface characteristics on infiltration rates and sediment production from interrill erosion from loam soil. Treatments were two different grass species (crested wheatgrass and intermediate wheatgrass), three levels of grass cover (30, 50, and 80 percent), four levels of rock cover (5, 10, 15, and 20 percent), and six levels of simulated trampling (10 to 60 percent of the respective plot area by 10 percent increments). Results indicated that plots with sod forming grass infiltrated only slightly more water than plots with bunchgrass, though the differences were significant. Trampling reduced infiltration rates significantly. On uncompacted soil, infiltration rates increased as percentage of rock cover increased. Trampling gradually destroyed this relationship however. Rock cover did not significantly affect sediment production. The tradeoff between vegetal cover and rock cover was affected by simulated trampling. Once trampling disturbance reached 20 percent, no relationship between vegetal cover and rock cover existed. Trampling was the most important factor influencing infiltration rates, explaining 35 to 48 percent of the variation in infiltration rates. The most important factor influencing sediment production was grass cover, which explained 40 to 62 percent of the variations associated with sediment yield at various trampling percentages. Results strongly suggest that, for slopes and soils as used here, adequate watershed protection may be obtained by maintaining 50 percent protective ground cover. Additional validation studies are recommended.     

DEEP PERCOLATION IN A SAND HILL AREA1

Records for two rivers flowing in a Sand Hill area are used to derive a value for the infiltration reaching the water table. The infiltration is 0.23 feet per year which is 13 per cent of the precipitation.     

污水地下渗滤系统基质床特性模拟

为提高污水地下渗滤系统(Subsurface Waste-water Infiltration System,SWIS)的生物脱氮效率,改进了基质床体结构组成,采用土柱模拟试验对比了基质床改进前后ORP特征及氨化、硝化及反硝化细菌数量的变化。结果表明,在地下渗滤系统中,氨氮的去除率(Q)随基质层深度的变化规律为Q(100 cm)Q(80 cm)Q(20 cm)≈Q(40 cm)Q(60 cm)。改进后基质铺设顺序依次为:0~60 cm填充炉渣和草甸棕壤(两者体积比为3∶7),60~130 cm铺设活性污泥、炉渣和草甸棕壤(三者体积比为1∶2∶7)。基质床结构组成改进后,20~60 cm区域氧化电位(ORP)大幅提高,尤其60 cm深度处ORP从0提高到180 m V,有效促进了硝化反应的进行;床体氨化、硝化及反硝化细菌数量大幅度提高,对NH+4-N及TN的脱除效率分别较改进前提高了12.6%和10.5%,出水NH+4-N及TN质量浓度满足城市景观地表水水质标准(GB/T 18921—2002)。