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COHYST Land Use Mapping

Using Satellite Imagery to Estimate Irrigated Land: A Case Study in Scotts Bluff and Kearney Counties, Summer 2002

INTRODUCTION

The year 2002 was the third driest for Nebraska in more than a century that records have been kept. Moderate to extreme drought conditions also reached across the High Plains and much of the West. At the height of the drought last summer, more than half of the country was affected. According to UNL climate impact specialist Mike Hayes, only the Dust Bowl years of 1934 and 1936 were drier in Nebraska than what was experienced in 2002.

The lack of moisture significantly affected agricultural production. The drought wiped out many dry land crops and forced growers to irrigate more than normal, which sent irrigation costs skyrocketing according to Tina Barrett, interim director of the Nebraska Farm Business Association at UNL. It was estimated that Nebraska’s agricultural losses from the 2002 drought was close to $1.2 billion.

THE STUDY AREA

Scotts Bluff and Kearney Counties were selected to represent different environments of the Cooperative Hydrology Study in the Central Platte River Basin (COHYST) study area. These counties have significant contrasts in topography, climate patterns and differences in the types of crops produced. The 1997 COHYST land cover classification identified variations in land cover. In 1997 over 59% of Kearney County was irrigated cropland, the majority of which was irrigated corn. In comparison, only 34% of Scotts Bluff County was irrigated cropland. These percentages, derived from an analysis of Landsat satellite imagery, compare with published figures from the 1997 Agricultural Census, which reported that 57% of Kearney County was irrigated cropland while 36% of Scotts Bluff County was irrigated cropland.
Both counties were strongly affected by the drought of 2002.

OBJECTIVES

The objective of this study is to test the accuracy of using satellite remote sensing techniques to estimate irrigated lands in Scotts Bluff and Kearney Counties during the summer of 2002. These results will supplement the research of the Cooperative Hydrology Study in the Central Platte River Basin (COHYST). COHYST is a multi-agency project intended to improve understanding of the hydrological conditions in the Central Platte River. COHYST is involved in the assemblage and creation of numerous geospatial data layers to be used in modeling and development of a water resources decision support system (DSS). Knowing the location and amount of irrigated lands is an important component of their modeling efforts.

Vegetation indices derived from satellite imagery provide an estimate of the health and vigor of agricultural crops. One of the most widely used vegetation indices, the Normalized Difference Vegetation Index (NDVI), was calculated to measure crop conditions during the summer of 2002. To aid in the classification, field data were collected in the fall of 2002 for Scotts Bluff and Kearney counties using Global Positioning System (GPS) to record the exact location of each field. Other information gathered at each location indicated the type of crop or land cover and if the field was or was not irrigated.

Datasets

Data
File Size
Metadata
Download Data*
     
Scotts Bluff County 2002 Irrigation Estimate
.8 MB
Kearney County 2002 Irrigation Estimate
.8 MB

*To download a file, right click on a link and select "save link as".

Data have been referenced to the State Plane Nebraska projection (Fipszone 2600) using the NAD83 datum and GRS 1980 spheroid. Data layers are provided compressed in a winzip file.

Technical Report
4.4 MB

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