Current frameworks for reference ET and crop coefficient calculation

Estimation of evapotranspiration is under continual development and evolution, with significant developments and standardizations made during the past three decades for both reference ET (ETref) and for crop coefficients (Kc). These standardizations provide consistency and reproducibility in estimating ETref and a consistent basis for determining and expressing Kc curves, especially at the local scale. The application of the dual Kc procedure is growing, and has strong potential for improving accuracy of ET estimates as compared to the single Kc approach. This article describes current structures for estimating crop coefficients including the standardized FAO-56 dual Kc approach, with example applications. Emphasis is placed on estimation of parameters and special cases to be considered. Newer bases for establishing Kcb curves include thermal units and vegetation indices

USCID fourth international conference

Presented at the Role of irrigation and drainage in a sustainable future: USCID fourth international conference on irrigation and drainage on October 3-6, 2007 in Sacramento, California.Includes bibliographical references.Evapotranspiration and net irrigation water requirements were determined for 123 weather station locations across the state of Idaho for available periods of record. Estimates were made for daily, monthly and annual timesteps. Updated methods were employed for calculating reference evapotranspiration (ETr) and crop coefficients (Kc). The ET estimates cover a wide range of agricultural crops grown in Idaho and, in addition, ET estimates have been made for a number of native plant systems including wetlands, rangeland, and riparian trees. Estimates have been made for evaporation from three types of open water surfaces ranging from deep reservoirs to small farm ponds. The ET and net irrigation water requirement calculations are intended for use in design and management of irrigation systems, for water rights management and consumptive water rights transfers and for hydrologic studies. ET calculations have been made for all times during the calendar year including winter to provide design and operation information for managing land application of agriculture, food processing and other waste streams. The weather stations evaluated include 107 National Weather Service (NWS) cooperative stations measuring primarily air temperature and precipitation and 16 AgriMet agricultural weather stations. The AgriMet stations measure a full complement of weather data affecting evapotranspiration and are located primarily in the southern part of the state. Estimates at many stations cover more than 80 to 100 year periods of air temperature data. Because only maximum and minimum air temperature are observed at the NWS cooperative stations, the solar radiation, humidity and wind speed data parameters required in the ASCE Penman-Monteith equation (ASCE-PM) were estimated similar to recommendations in ASCE-EWRI (2005) where estimates for solar radiation (Rs) were based on differences between daily maximum and minimum air temperature and estimates for daily dewpoint temperature were based on daily minimum air temperature. Estimates for wind speed were based on long-term mean monthly summaries from AgriMet stations in southern Idaho and some airport locations in central and northern Idaho. Crop evapotranspiration, abbreviated ETc, was calculated on a daily timestep basis for improved accuracy. Daily calculation timesteps allowed for the calculation of evaporation of water from wet soil surfaces following precipitation or irrigation events. ETc for monthly, growing season and annual periods were summed from the daily calculations. Basal crop coefficient curves were developed or organized for 42 crop and land-cover types. Scheduling of irrigations was simulated to estimate soil evaporation from irrigation wetting events using a root-zone water balance

Applying the FAO-56 Dual \u3ci\u3eK\u3csub\u3ec\u3c/sub\u3e\u3c/i\u3e Method for Irrigation Water Requirements over Large Areas of the Western U.S.

The FAO-56 dual crop coefficient procedure was used to determine evapotranspiration (ET) and net irrigation water requirements for all agricultural areas of the states of Idaho and Nevada and in a western U.S. study on effects of climate change on future irrigation water requirements. The products of the applications are for use by state governments for water rights management, irrigation system planning and design, wastewater application system design and review, hydrologic water balances, and groundwater modeling. The products have been used by the U.S. federal government for assessing impacts of current and future climate change on irrigation water demands. The procedure was applied to data from more than 200 weather station locations across the state of Idaho, 200 weather station locations across the state of Nevada, and eight major river basins in the western U.S. for available periods of weather records. Estimates were made over daily, monthly, and annual time intervals. Methods from FAO-56 were employed for calculating reference ET and crop coefficients (Kc), with ET calculations performed for all times of the calendar year including winter. Expressing Kc as a function of thermal-time units allowed application across a wide range of local climates and elevations. The ET estimates covered a wide range of agricultural crops grown in the western U.S. plus a number of native plant systems, including wetlands, rangeland, and riparian trees. Evaporation was estimated for three types of open-water surfaces ranging from deep reservoirs to small farm ponds

Sensitivity of evapotranspiration retrievals from the METRIC processing algorithm to improved radiometric resolution of Landsat 8 thermal data and to calibration bias in Landsat 7 and 8 surface temperature

We made an assessment on the use of 12-bit resolution of Landsat 8 (L8) on evapotranspiration (ET) retrievals via the METRIC process as compared to using 8-bit resolution imagery of previous Landsat missions. METRIC (Mapping Evapotranspiration at high Resolution using Internalized Calibration) is an ET retrieval system commonly used in water and water rights management where the surface energy balance process is coupled with an extreme- end point calibration process to remove most impacts of systematic bias in remotely sensed inputs. We degraded L8 thermal images by grouping sequential digital numbers to reduce the apparent numerical resolution and then recomputed ET using METRIC and compared to nondegraded ET products. The use of 8-bit thermal data did not substantially impair the accuracy of ET retrievals derived from METRIC, as compared to the use of 12-bit thermal data. The largest error introduced into ET was \u3c1%. We also compared ET retrieved from images processed during the L8 and Landsat 7 (L7) March 2013 underfly to assess differences in ET caused by differences in signal to noise ratio (SNR) and scaling of the two systems. We evaluated the impact of bias in land surface temperature (LST) retrievals on ET determination using the CIMEC calibration approach (Calibration using Inverse Modeling using Extreme Member Calibration) employed in METRIC by introducing globally systematic biases into LST retrievals from L7 and L8 and comparing to ET from non-biased retrievals. The impacts of the introduction of both additive and multiplicative biases into surface temperature on ET were small for the three regions of the US studied, and for both L7 and L8 satellite systems. An independent study showed that METRIC-produced ET compared to within 3% of measured ET for the California site. The study assessed the impact of the February 2014 recalibration of L8 thermal data that caused a 3 K downward shift in LST estimation and changed reflectance values by about 0.7%. We found that the use of the recalibrated LST and shortwave data sets in METRIC did not change the accuracy of ET retrievals due to the automatic compensation for systematic biases employed by METRIC

METRIC-GIS: An advanced energy balance model for computing crop evapotranspiration in a GIS environment

A novel ArcGIS toolbox that applies the Mapping Evapotranspiration with Internalized Calibration model was developed and tested in a semi-arid environment. The tool, named METRIC-GIS, facilitates the pre-processing operations and the automatic identification of potential calibration and pixels review. The energy balance components obtained from METRIC-GIS were contrasted with those from the original METRIC version (R2 = 1; RMSE = 0 W m–2 or mm day–1 for ETc) Additionally, an irrigated scheme located at southern Spain was considered for assessing Kc variability in the maize fields with METRIC-GIS. The identified spatial variability was mainly due to differences in irrigation regimes, crop management practices, and planting and harvesting dates. This information is critical for developing irrigation advisory strategies that contribute to the area sustainability. The developed tool facilitates data input introduction and reduces computational time by up to 50%, providing a more user-friendly alternative to other existing platforms that use METRIC

Comparison of Latent Heat Flux Using Aerodynamic Methods and Using the Penman–Monteith Method with Satellite-Based Surface Energy Balance

A surface energy balance was conducted to calculate the latent heat flux (λE) using aerodynamic methods and the Penman–Monteith (PM) method. Computations were based on gridded weather and Landsat satellite reflected and thermal data. The surface energy balance facilitated a comparison of impacts of different parameterizations and assumptions, while calculating λE over large areas through the use of remote sensing. The first part of the study compares the full aerodynamic method for estimating latent heat flux against the appropriately parameterized PM method with calculation of bulk surface resistance (rs). The second part of the study compares the appropriately parameterized PM method against the PM method, with various relaxations on parameters. This study emphasizes the use of separate aerodynamic equations (latent heat flux and sensible heat flux) against the combined Penman–Monteith equation to calculate λE when surface temperature (Ts) is much warmer than air temperature (Ta), as will occur under water stressed conditions. The study was conducted in southern Idaho for a 1000-km2 area over a range of land use classes and for two Landsat satellite overpass dates. The results show discrepancies in latent heat flux (λE) values when the PM method is used with simplifications and relaxations, compared to the appropriately parameterized PM method and full aerodynamic method. Errors were particularly significant in areas of sparse vegetation where differences between Ts and Ta were high. The maximum RMSD between the correct PM method and simplified PM methods was about 56 W/m2 in sparsely vegetated sagebrush desert where the same surface resistance was applied

Connecting People and Place Prosperity: Workforce Development and Urban Planning in Scholarship and Practice

In recent years, the field of workforce development has emerged as a distinct area of policy and practice. While planning scholars have begun to engage with the workforce development field, its relevance and points of connection to planning scholarship remain underexplored. This article attempts to define the workforce development field by articulating its core concerns as well as its domains of practice and scholarship outside the planning field. The article locates workforce development within three stands of planning scholarship, concluding that workforce development represents an important bridge for planners between “place” and “people” prosperity within communities