Andy Ward

MANIPULATION OF HIGH SPATIAL RESOLUTION AIRCRAFT REMOTE SENSING DATA FOR USE IN SITE-SPECIFIC FARMING

Three spatial data sets consisting of high spatial resolution (1 m) remote sensing images acquired in 12 spectral bands, an on-the-go yield map, and a Digital Elevation Model were co-registered and evaluated for spatial variability studies in a Geographic Information Systems environment. Separate on-the-go yield maps were developed for 3, 5, and 12 statistically significant mean yield classes. For each yield class, the corresponding mean spectral and elevation data were extracted. The relationship between mean spectral and yield data was strongly linear (r = 0.99). Also, a strong linear relationship between mean yield and elevation data (r = 0.92) was found. The relationship between the spectral and on-the-go yield data indicated the potential of remote sensing for spatial variability studies. Keywords. Remote sensing, GIS, On-the-go yield, DEM, Precision farming.

EVALUATING CHANNEL-FORMING DISCHARGES: A STUDY OF LARGE RIVERS IN OHIO

Measured data were used to evaluate whether bankfull discharges were related to effective discharges for large rivers in Ohio. The frequency and sediment transport associated with these channel-forming discharges was also examined. Rural watersheds in the Midwest region of the U.S. are dominated by agricultural land uses that incorporate subsurface drainage improvements. Bankfull discharges were determined by measuring fluvial features at each USGS gage and then relating these features to the rating curve and historic daily discharge data for each gage. Effective discharges were determined by using suspended sediment data obtained at the gages, the Wolman-Miller method for calculating geomorphic work, and bin sizes based on stage intervals to group sediment and discharge data. There was good agreement between the effective discharge and bankfull discharge estimates. Bankfull and effective discharges were primarily related to flows that transported the middle 50% of the total sediment load. Recurrence intervals of the bankfull and effective discharges ranged from 0.3 to 1.4 years. These recurrence intervals are more frequent than generally reported in the literature. The duration of daily discharges that equaled or exceeded the channel-forming discharge ranged from 1 to 24 days annually, with mean values of 9 and 11 days for the bankfull discharge and effective discharge, respectively. Common methods for determining the recurrence interval are inadequate for frequent channel-forming discharges, and better insight is obtained by determining the number of days on which these flows are exceeded annually.

Effects of geomorphology, habitat, and spatial location on fish assemblages in a watershed in Ohio, USA

In this paper, we evaluate relationships between in-stream habitat, water chemistry, spatial distribution within a predominantly agricultural Midwestern watershed and geomorphic features and fish assemblage attributes and abundances. Our specific objectives were to: (1) identify and quantify key environmental variables at reach and system wide (watershed) scales; and (2) evaluate the relative influence of those environmental factors in structuring and explaining fish assemblage attributes at reach scales to help prioritize stream monitoring efforts and better incorporate all factors that influence aquatic biology in watershed management programs. The original combined data set consisted of 31 variables measured at 32 sites, which was reduced to 9 variables through correlation and linear regression analysis: stream order, percent wooded riparian zone, drainage area, in-stream cover quality, substrate quality, gradient, cross-sectional area, width of the flood prone area, and average substrate size. Canonical correspondence analysis (CCA) and variance partitioning were used to relate environmental variables to fish species abundance and assemblage attributes. Fish assemblages and abundances were explained best by stream size, gradient, substrate size and quality, and percent wooded riparian zone. Further data are needed to investigate why water chemistry variables had insignificant relationships with IBI scores. Results suggest that more quantifiable variables and consideration of spatial location of a stream reach within a watershed system should be standard data incorporated into stream monitoring programs to identify impairments that, while biologically limiting, are not fully captured or elucidated using current bioassessment methods.

Comparison of Daily Water Table Depth Prediction by Four Simulation Models

The Agricultural Drainage And Pesticide Transport (ADAPT) model was compared to the water management simulation models DRAINMOD, SWATREN, and PREFLO. SWATREN and PREFLO are one-dimensional finite-difference models while ADAPT and DRAINMOD are one-dimensional mass balance models. ADAPT, an extension of the computer model GLEAMS, also provides chemical transport information. All four models were tested against field data from Aurora, North Carolina. Observed water table depth data were collected during 1973 through 1977 from a water table management field experiment with three subsurface drain spacing treatments of 7.5, 15, and 30 m.

THE SENSITIVITY OF ADAPT MODEL PREDICTIONS OF STREAMFLOWS TO PARAMETERS USED TO DEFINE HYDROLOGIC RESPONSE UNITS

The responses of ADAPT, a daily water table management simulation model, to variations in the principal input parameters which define hydrologic response units on a watershed was evaluated. The study was conducted on a small agricultural watershed in Ohio. The results suggest that useful estimates of monthly flows could be obtained by using NRCS soils information, land use, and tillage information estimated from Landsat TM data, a 30-meter digital elevation model, and readily available information on the prevailing farming systems. Water quality and quantity responses were sensitive to combinations of the slope, soil type, land use, tillage, crop rotations, and drainage practice and should be taken into account in defining the hydrologic response units. The sediment load predictions were sensitive to the field size. Approximations of when planting occurred did not affect the flow and sediment predictions but had an impact on nitrate and pesticide predictions.

A COMPARISON OF FOUR FIELD METHODS FOR MEASURING SATURATED HYDRAULIC CONDUCTIVITY

A comparison was made of the Guelph permeameter, the velocity permeameter, a pumping test procedure, and the auger hole method for measuring saturated hydraulic conductivity. The methods were compared on a Ravenna silt loam and a Hoytville silty clay loam. The evaluations were conducted during high water table conditions established by subirrigation. All the methods showed a wide variability in saturated hydraulic conductivity within each research plot. The pumping test, auger hole, and velocity permeameter methods provided results within similar ranges whereas the Guelph permeameter provided significantly lower estimates. Saturated hydraulic conductivity estimates for the Ravenna silt loam ranged from 0.03 to 35 mm/h with an average value of 3.4 mm/h. Estimates for the Hoytville silty clay loam ranged from 0.01 to 260 mm/h with an average value of 2.2 mm/h.

ADAPT: Model Use, Calibration, and Validation

This article presents an overview of the Agricultural Drainage and Pesticide Transport (ADAPT) model and a case study to illustrate the calibration and validation steps for predicting subsurface drainage and nitrate-N losses from an agricultural system. The ADAPT model is a daily time step, field-scale water table management model that was developed as an extension of the GLEAMS model. The GLEAMS algorithms were augmented with algorithms for subsurface drainage, subsurface irrigation, deep seepage, and related water quality processes. Recently, a frost depth algorithm was incorporated to enhance the model’s capability to predict flow during spring and fall months. In addition to the normal GLEAMS output, ADAPT gives estimates of pesticides and nutrients in drainage. The model has four components: hydrology, erosion, nutrient transport, and pesticide transport. Predictions of surface runoff and subsurface drainage by ADAPT are very sensitive to hydrology input parameters, such as NRCS curve number, hydraulic conductivity, depth of the impeding layer, and hydraulic conductivity of the impeding layer. In the erosion component, slope, hydraulic length, and crop management are the most sensitive factors. Nutrients generally follow the trends in surface runoff and subsurface drainage. In addition, nitrogen and phosphorus concentrations in soil horizons are sensitive to nutrient losses. Recently, the ADAPT model was further calibrated and validated in southern Minnesota to evaluate impacts of subsurface drain spacing and depth, rate and timing of nitrogen application, and precipitation changes on water quality. ADAPT is written in FORTRAN, and the source code is available to interested model users. Considering the limited technical support and text editor-based input files, development of a user-friendly interface to create input files would greatly enhance ADAPT’s acceptability by users involved in modeling agricultural systems equipped with subsurface drains.

Atrazine and alachlor dissipation rates from field experiments

Chemical transport is being monitored in the root zone of three agricultural management systems at the Ohio Management Systems Evaluation Area (OMSEA). Atrazine and alachlor concentration data from soil cores taken to a depth of 0.9 m and partitioned into the increments of 0.0 to 0.15, 0.15 to 0.3, 0.45 to 0.6, and 0.75 to 0.9 m show the herbicides remained in the top 0.15 m of the profile during the 1991 and 1992 growing seasons. The slow movement of herbicides was partly due to below normal rainfall during the period. Since the herbicides have not been transported out of the soil profile, dissipation rates could be determined from the field observations.

Spreadsheet Tools for River Evaluation, Assessment and Monitoring: The STREAM Diagnostic Modules

Stream physical condition is increasingly a priority for resource managers. Assessment, monitoring and restoration techniques continue to be developed and standardized. A suite of spreadsheet tools, the STREAM Modules, has been developed by the Ohio Department of Natural Resources and Ohio State University to meet the technical demand. This ongoing project began in 1998 and includes the following modules that are available at no cost: 1) Reference Reach Spreadsheet for reducing channel survey data and calculating basic bankfull hydraulic characteristics, 2) Regime Equations for determining the dimensions of typical channel form, 3) Meander Pattern that dimensions a simple arc and line best fit of the sine-generated curve, 4) Two-Stage Geometry that sizes a two-stage channel system based on regional curves and provides estimates of earthwork requirements to construct various two-stage geometries, 5) Sediment Equations which includes expanded and condensed forms of critical dimensionless shear, boundary roughness and common bed load equations, 6) Effective Discharge that, based on historic data from USGS stream gages, develops a Wolman-Miller geomorphic work plot and contains several methods for calculating the geomorphic work and the effective discharge, 7) Lane Balance educational tool, and 8) Contrasting Channels that computes hydraulic and bed load characteristics in a side-by-side comparison of two channels of different user defined forms. An overview of each module will be presented together with example applications.

Sizing Stream Setbacks to Help Maintain Stream Stability

The objectives of the study were: (1) to evaluate the ability of an empirically based equation to predict the streamway width required to allow a stream to self-adjust its meander pattern; (2) to evaluate the influence of urbanization, floodplain width, and incision on bed load transport, the size of particle moved at incipient motion at flows approximating the effective discharge, and flood stage for the 100 year recurrence interval event; and to determine if knowledge obtained from Objectives 1 and 2 could be used to develop stream setback guidelines that would help avoid channel instability problems typically associated with urbanization. Empirical and practical theoretical methods were used on 6 watersheds in central Ohio. The results showed that the extent of the meander pattern for all of the watersheds was well represented by the empirical streamway width equation. An analysis of flow and bed load transport in a compound two-stage channel was performed for a series of different magnitude events that might occur during a 100 year period. The results showed that 1) floodplain width reduction, 2) entrenchment and 3) changes in flow regime each had a high potential to increase bed load transport and collectively changes in all these factors could result in a five to fifteen fold increase. The recommended approach is to establish setbacks that are a function of the meander belt width as calculated by an empirical equation that is based on the drainage area. Also, land uses within the setback zone should be restricted to uses that sustain or enhance the ecological function of the system and accommodate the stream in a state of dynamic equilibrium. Based on a previous study by the authors it is also recommended that storm water management strategies be used expressly to control bed load sediment transport rates.