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Publications (49)
The ASCE Evapotranspiration in Irrigation and Hydrology Committee in cooperation with the Water Management Committee of the Irrigation Association has defined and established a standardized reference evapotranspiration (ET) equation. The purpose of the equation and standardized calculation of parameters is to bring a commonality to the methodology...
Program outcomes are defined by ABET as narrow statements that describe the skills that students should possess at the time of graduation. ABET specifies a set of outcomes that should be met by all engineering programs. In order to demonstrate that the curriculum adequately meets specific program criteria, one alternative is to define additional ou...
Soil moisture is an important component in many hydrologic and land–atmosphere interactions. Understanding the spatial and temporal nature of soil moisture on the mesoscale is vital to determine the influence that land surface processes have on the atmosphere. Recognizing the need for improved in situ soil moisture measurements, the Oklahoma Mesone...
Established as a multipurpose network, the Oklahoma Mesonet operates more than 110 surface observing stations that send data every 5 min to an operations center for data quality assurance, product generation, and dissemination. Quality-assured data are available within 5 min of the observation time. Since 1994, the Oklahoma Mesonet has collected 3....
Current methods of determining nitrogen (N) fertilization rates in winter wheat (Triticum aestivum L.) are based on farmer projected yield goals and fixed N removal rates per unit of grain produced. This work reports on an alternative method of determining fertilizer N rates using estimates of early-season plant N uptake and potential yield determi...
Continued development of networks of electronic weather stations worldwide has increased the availability of weather data for calculating ETo on an hourly basis. There has been question and debate as well as studies on the appropriate expression and parameterization for the surface resistance (rs) parameter of the Penman-Monteith (PM) equation and...
Comparison among commonly used reference evapotranspiration (ET) equations in the United States and the recently recommended ASCE standardized reference ET equation was made as part of the ASCE standardization effort. Analyses used hourly and daily weather data from 49 geographically diverse sites in the United States. Calculations were performed f...
Soil moisture is an important hydrologic variable of great consequence in both natural and agricultural ecosystems. Unfortunately, it is virtually impossible to accurately assess the spatial and temporal variability of surface soil moisture using conventional, point measurement techniques. Remote sensing has the potential to provide areal estimates...
As surface exchange processes are highly non-linear and heterogeneous in space and time, it is important to know the appropriate scale for the reasonable prediction of these exchange processes. For example, the explicit representation of surface variability has been vital in predicting mesoscale weather events such as late-afternoon thunderstorms i...
A network of automated soil water and temperature systems, installed at 21 locations in Oklahoma and Kansas in 1996 and 1997, is providing hourly profiles of soil temperature and water at eight depths, from 0.05 to 1.75 m below the surface, in twin profiles 1 m apart. Dubbed the Soil Water and Temperature System (SWATS), these systems are an additi...
This paper addresses the refinement and testing of a simple downwelling longwave radiation model. Oklahoma atmospheric surface-layer instrumentation system (OASIS) radiation data in combination with Oklahoma Mesonet weather data were used to evaluate various techniques for estimating downwelling longwave radiation, for daytime and nighttime as well...
Oklahoma Atmospheric Surface-Layer Instrumentation System (OASIS) measurements of net radiation (Rn), latent heat flux (LH), sensible heat flux (SH), and ground heat flux (GH) were used to validate the NOAH-Oregon State University Land Surface Model (NOAH-OSU LSM). A 1-year study period was used. Rn, LH, SH and GH data from seven sites were screene...
A combination of high temporal resolution Advanced Very High Resolution Radiometer (AVHRR) data and high spatial information Map Information Analysis and Display System (MIADS) landuse/landcover data from the United States Department of Agriculture-Natural Resources Conservation Service (USDA-NRCS) were used to investigate the feasibility of using...
Modeling of land surface processes in the context of coupled land-atmosphere prediction
has advanced over the last decade with the development of many sophisticated models that
represent a concentration of effort by researchers from disciplines such as hydrology, climate
modeling and ecology. The variable infiltration capacity (VIC) land surface mo...
The ASCE Evapotranspiration in Irrigation and Hydrology Committee (ASCE-ET) is recommending, for the intended purpose of establishing uniform evapotranspiration (ET) estimates and transferable crop coefficients, two Standardized Reference Evapotranspiration Surfaces: (1) a short crop (similar to grass) and (2) a tall crop (similar to alfalfa), and...
Root zone salinity is one of the major factors adversely affecting crop production. A saline shallow water table can contribute significantly to salinity increases in the root zone. A soil salinity model (LEACHC) was used to simulate the effects of various management alternatives and initial conditions on root zone salinity, given a consistently hi...
A combination of high temporal resolution Advanced Very High Resolution Radiometer (AVHRR) data (1000 m), and high spatial resolution landuse/landcover data (200 m) from the Oklahoma Natural Resources Conservation Service (NRCS) were used to investigate the temporal and spatial dynamics of Oklahoma vegetation. The dates and relative magnitudes for...
A set of neural networks, each of which predicts soil water content at a given depth as a function of soil temperature, has been developed. Networks were developed to predict at depths of 0.15 m, 0.3 m, 0.6 m, and 1.2 m. Input data consists of a coefficient describing soil type and soil temperatures measured at two depths above and two depths below...
An integrated approach to reservoir, irrigation, and cropping management which links four different models—a hydrologic model (PRMS), a crop growth simulation model (EPIC), an economic model based on linear programming, and a dynamic programming model—is developed and demonstrated. The demonstration is based on an irrigation district located in a s...
Nitrogen losses in runoff and leaching from crop production for the 110 counties over the Ogallala aquifer in the High Plains region are estimated. Cropland distribution by crop, soil, irrigation system, and rotation practice is estimated using the 1992 National Resources Inventory database. Nitrogen runoff and leaching are simulated using the EPIC...
The Oklahoma mesonet is a joint project of Oklahoma State University and the University of Oklahoma. It is an automated network of 108 stations covering the state of Oklahoma. Each station measures air temperature, humidity, barometric pressure, wind speed and direction, rainfall, solar radiation, and soil temperatures. Each station transmits a dat...
intense convective storms developed along the dryline over the Oklahoma Panhandle. Over the eastern panhandle and northwestern Oklahoma, the pre-convective environment was characterized by moderate static instability and the presence of a deep CBL, resulting from strong solar heating. GOES sounding profiles at Liberal, Kansas and a meteogram from B...
Bed and basin tillage practices are presented for wide bed cultivation under LEPA irrigation systems. Practices were selected to contain irrigation and rainfall water at the point of application for linear crop rows under a LEPA equipped center-pivot system. The grain sorghum crop was planted in two crop rows on top of 1.42 m (56 in.) wide beds. Th...
Targeting certain soils and cropping systems may be necessary in consideration of regional water quality protection policies. However, little information is available relating soils and cropping practices to regional water quality problems. This study evaluates crop yield and NO3-N movement to surface and groundwater on four soils and nine principa...
Selection of the variables to be measured and specification of the sensors to make those measurements are two important issues in the implementation of an automated weather station network. Design decisions are reviewed in the context of the Oklahoma Mesonet, a state-wide network serving multiple purposes and consisting of more than 100 remote stat...
A three-stage modeling framework is applied to evaluate the potential economic and environmental impacts of agricultural groundwater protection policies in the Central High Plains Region. Three alternative policies (limitations on total nitrogen applications, limitations on unit-area nitrogen applications, and restrictions on the use of selected he...
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 simula...
Peanuts (Arachis hypogaea L.) were grown in the field under both well-irrigated and limited-irrigation conditions. On four different sampling dates, root length density (RLD) data were obtained at eight depths and in three locations relative to the crop row. The RLD tended to be substantially greater at shallow depths in the crop row, and to be mor...
The need for a mathematical model capable of simulating simultaneously the effects of different agricultural management practices on crop yield, and chemical (nutrients and pesticides) losses by surface runoff, sediment movement and leaching below the rootzone has prompted the development of EPIC-PST. This model was developed by using EPIC as a bui...
A portable eddy correlation system was used to make direct, real-time measurements of evapotranspiration over irrigated alfalfa. The surface energy balance equation was used to evaluate system performance, with the closure ratio defined as the ratio of the sum of latent and sensible heat fluxes to the sum of net radiation and soil heat flux. For si...
The Penman equation for estimating hourly evapotranspiration (ET) of an alfalfa reference crop was calibrated for both daytime and nighttime conditions. Hourly net radiation, sensible heat flux, and soil heat flux were measured in the field for 16 24-hr periods, and evaporative flux was determined as the residual of the surface energy balance equat...
Irrigation schedules for grain sorghum in the Panhandle of Oklahoma were determined using a cost/loss risk analysis (C/L) procedure, a crop growth simulation model, and rainfall forecasts. Ten rainfall probability sequences were investigated. Whenever the C/L ratio reached a critical level, as determined by the probability of rainfall, irrigation w...
Meteorological and soil moisture data were collected from field sites in Caddo County, Oklahoma, during the 1984 and 1985 irrigation seasons. Analysis of alfalfa (Medicago sativa L.) water use data enabled calibration of the modified Penman equation for reference crop evapotranspiration (et). A crop coefficient relationship for Spanish peanuts (Ara...
Two simple models are developed to predict the advance rate of flow in furrows. The first model is developed using a modified version of Muskingum flood-routing techniques. The second model is developed by assuming that the flow is approximately steady within each furrow reach. Both models use power functions to describe the surface and subsurface...
Growth simulation models provide potential benefit in the study of peanut (Arachis hypogaea L.) production. Two physiologically-based peanut simulation models of varying complexity were adapted and calibrated to simulate the growth and yield of Spanish peanut under Oklahoma conditions. Field data, including soil moisture measurements and sequential...
A method is presented for using dimensionless advance curves and furrow irrigation field data to derive the values of the modified Kostiakov infiltration parameters. Analysis of data from Colorado furrows indicated that infiltration can be greatly influenced by furrow compaction and by variability through an irrigation season.-Authors
A set of five dimensionless parameters was devrived by normalizing the zero-inertia equations governing the rate of water advance in furrow irrigation. Dimensionless advance was found to be insensitive to the two dimensionless furrow geometry parameters. The remaining three parameters, which all related to infiltration, were then varied in order to...
The rate of advance of the water front in furrows was mathematically modelled using a zero-inertia approach, in which the surface water hydraulics were simplified by neglecting accelerations. Power curve relationships are used to relate both the flow depth and wetted perimeter to the cross-sectional flow area. Infiltration is described with the mod...
Linear, normal, and beta statistical models are fit to 2,450 overlapped sprinkler irrigation patterns. The deviations of these three models from the observed water distribution are compared. Of the three, the beta distribution provides the best fit but is presently least practical to use. For uniformity coefficients above about 0. 65, the normal mo...
A soil water balance model was developed to predict days available for soil tillage in Illinois during the spring months. The model was tested against field work days data from the Illinois Cooperative Crop Reporting Service and local daily field observations of favorable work days. The accuracy of the model was found to be sufficient to predict av...
Exchanges of water and energy between the surface of the earth and the atmosphere occur continuously. However, modeling these exchanges poses great challenges for many reasons. Recently there has been a focus on physically-based modeling of the surface exchange processes from both hydrological and atmospheric science perspectives. Modeling of land...
The Oklahoma Mesonet, a statewide automated network of more than 110 environmental monitoring stations, has proven to be very useful to the state's water management functions at both the wet and dry ends of the hydrological spectrum.
