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Projected Crop Acres - Details and Data
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Baseline Irrigated Area:Mapped irrigation fields formed the baseline acreage from which future years' irrigated area projections were made. Several sources of GIS-based data provided a maps for each county's irrigated areas. In many cases, they allowed identification of type of irrigation system or and type of crop being irrigated: |
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The Agricultural Permitting Unit of the Georgia Department of Natural Resources Environmental Protection Division provided GIS records from their permit application and mapping efforts, both done with farmer help.
The Agricultural Water Conservation and Metering Program of the Georgia Soil and Water Conservation Commission provide GIS maps used in establishing irrigation metering.
The Flint River Water Planning and Policy Center of Albany State University, a contractor to GaSWCC, provided maps based on field visits and assisted in filling gaps of other records. |
| All of these map records were carefully combined to eliminate duplicates and correct for field changes since original mapping was done. Finally, new irrigated areas were identified through examination of aerial imagery at The University of Georgia's National Environmentally Sound Production Agricultural Laboratory. With the cooperation of these agencies and research teams, we were able to compile a comprehensive statewide inventory and map of Georgia's irrigated land. |
| Further Details.
For more complete explanations of procedures used in mapping baseline irrigation area.
Data Sets:
Conference publication
Georgia Water Resources Conference paper describing these and former irrigation mapping efforts in Georgia
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Projected Crop Acreage - Major and Specialty Crops: |
Future irrigation of specific crops on Georgia's cropland depends upon many factors. We considered econometric factors driving production decisions and not those that could arise from land use or water use restrictions.
Projected acreage for the five crops that cover the largest expanse of irrigated land in Georgia were based on models adapted for this study by UGA economists. These projections included cotton, peanut, corn, soybean and pecan. Additionally, projections were made for vegetables in two categories - fresh market and processing. Predicted acreage for each was taken as an average of three projections made by three econometric models - National, Southeastern, Georgia. Details of the forecast models and their sources of data are discussed in more detail HERE.
The National model begins with 10-year planting projections made by by the United States Department of Agriculture (USDA). Corn, cotton, and soybean forecasts are released every year by USDA for the upcoming ten years. Similarly tree nuts, which include pecans, are projected by USDA as part of their broader categories of Fruits and Nuts. The USDA does not make 10-year projections for individual vegetables, but they broadly project pounds of produce for the fresh market and pounds of produce for the processing market. To use this data in pounds, we assumed that the production per acre would not change appreciably over the Ag Water Demand projection period. Thus growth rate in pounds would be equivalent to growth rate in acres. Since USDA does not make national projections for peanut, data from the Food and Agricultural Policy Research Institute (FAPRI) was used. Growth (or declines) in planted acres beyond the 10-year USDA and FAPRI figures assumed that the long range forecast that forms the basis of the latter years (2015, 2016, & 2017) of USDA's forecast would continue through 2050. Since USDA's forecasts are updated every year to reflect current market, political, and weather conditions, these Ag Water Demand forecasts can be updated later to better reflect conditions in the future.
Two other econometric models were also used. Projections were made for corn, cotton, soybean, and peanut using the acreage response elasticities for the Southeast Region (USDA, 1996). Then, the elasticity estimates from Mullen et al. were used to generate projections for corn, cotton, peanuts, and soybeans in Georgia. In both of these cases, projected prices from USDA through 2018 were applied to the acreage response elasticities. Elasticities reflect responses to prices actually received locally (Southeast and Georgia). With these regional and state models, we gain greater local response in projections. With the three models were averaged, we create an average track for Georgia's future plantings of irrigated crops.
Irrigated land was not held constant in our projections; we assumed that irrigation growth would occur as in past years, and that acreage increases would occur in counties that already had well-developed irrigated farming practices. The infrastructure that supports specialty crops like peanut and cotton, as well as other crops would lead to expansion where those crops already are produced efficiently. Both the mapping of irrigated land and casual observations by county agents and irrigation specialists points to evidence that much of this infilling is already occuring. Center pivots are being rearranged, and corners and smaller fields are being covered with smaller pivots, even when that means that the pivot cannot be used in full circle operation. Land for irrigation growth is expected to come primarily from non-irrigated cropland and pastures, although in some counties, growth in recent years has included land where timber was harvested.
Econometric projections for many of Georgia's specialty crops were beyond the scope of this study. Too little long range data is available for most of them. However, these specialty crops are grown and irrigated. We wanted to include water demand created by these crops. Areas of irrigated blueberry, peach, grapes, plant nurseries, drip irrigated vegetables and sod production could clearly be seen in aerial images, and those areas were included in our baseline acreage.
Our approach for projecting future plantings of specialty crops was to assume that they would continue to be produced where they are already established. Counties producing these were documented through the CES Irrigation Surveys; the 2008 survey data was used for the baseline. Growth rate for vegetables acreage was projected as described above using the National model. For tobacco, blueberry, peach, as well as the ornamental crops - turfgrass sod, plant nurseries, and production greenhouses, we used the average growth rate of all other crops in Georgia.
Projected irrigated areas were computed for Georgia as a whole. To disaggregate the data - split it into counties and river basins - we used the 2008 mapped area locations and the 2008 CES Irrigation Survey. The maps told us where the current irrigated fields were located. The Irrigation Surveys told us the proportions of irrigated acres by crop types. For example if 1000 irrigated acres was mapped in one portion of the county, and that county's survey numbers showed 70 percent cotton and 30 percent peanut in production, the baseline for the county was 700 acres of cotton and 300 acres of peanut. Future growth was projected from those starting numbers. If no vegetables were reported in the survey, future projections would show no vegetables there as well.
No adjustments were made for non-agricultural growth that could lead to competition for irrigated land. Future adjustments will have to consider impacts of urban and suburban encroachment on farm lands in selected counties. This can best be accommodated by examination of local growth projections. |
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Last updated 9/23/2010 James E. Hook |
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