DGS Reports of Investigations

Permanent URI for this collection

https://udspace.udel.edu/handle/19716/2521

Browse

Browsing DGS Reports of Investigations by Author "DeLiberty, T.L."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Estimating Evapotranspiration for 2016 Growing Season Using Landsat 8 Data and Metric Model in Sussex County, Delaware
    (Newark, DE: Delaware Geological Survey, University of Delaware, 2023-08) He, C.; Andres, A.S.; Brinson, K.R.; DeLiberty, T.L.
    Evapotranspiration (ET) is a major part of the water cycle. Reliable measurements or estimates of ET can greatly improve quantitative forecasts and hindcasts of water demand by crops, horticulture, and natural vegetation, and also help to manage and conserve water resources. Direct measurement of ET requires not only specific devices such as eddy covariance instruments, but also well-trained research personnel to collect accurate data. As a result, a variety of indirect methods for estimating ET have been developed in recent decades. Among them, remote sensing methods have proved cost-effective in providing accurate regional and global coverage of ET. In Sussex County, Delaware’s leading county in crop production, the ET distribution for the 2016 growing season was estimated using the Mapping Evapotranspiration at high Resolution with Internalized Calibration method, an energy-balance based ET mapping tool that utilizes satellite images and weather data. The estimated result was compared with field measurements using an eddy covariance instrument. The total estimated ET during Sussex County’s growing season (May-September) in 2016 accounts for 77 to 87 percent of historical-averaged annual ET in this region. The model-simulated seasonal ET for agricultural land is about 33 percent higher than urban/suburban areas and about 22 percent lower than forested areas. This study shows that when forestlands are converted to urban/suburban uses, significant amounts of water are diverted from ET and are then available to run off and/or infiltrate. Given that urban/suburban land has impervious surfaces in the forms of rooftops, roads, driveways, parking lots, sidewalks, etc., much of the water not lost to the atmosphere through ET presumably becomes part of the surface runoff portion of the water budget, thus underscoring the need for adequate storm-water management systems for urban/suburban lands. The results also imply that the practice of ET-based irrigation scheduling could be valuable in Sussex County and throughout the 20 percent of Delaware farmland that is irrigated.
  • Thumbnail Image
    Item
    Locating Ground-Water Discharge Areas In Rehoboth And Indian River Bays And Indian River, Delaware Using Landsat 7 Imagery
    (Newark, DE: Delaware Geological Survey, University of Delaware, 2008) Wang, L.T.; McKenna, T.E.; DeLiberty, T.L.
    Delaware’s Inland Bays in southeastern Sussex County are valuable natural resources that have been experiencing environmental degradation since the late 1960s. Stresses on the water resource include land use practices, modifications of surface drainage, ground-water pumping, and wastewater disposal. One of the primary environmental problems in the Inland Bays is nutrient over-enrichment. Nitrogen and phosphorous loads are delivered to the bays by ground water, surface water, and air. Nitrogen loading from ground-water discharge is one of the most difficult to quantify; therefore, locating these discharge areas is a critical step toward mitigating this load to the bays. Landsat 7 imagery was used to identify ground-water discharge areas in Indian River and Rehoboth and Indian River bays in Sussex County, Delaware. Panchromatic, near-infrared, and thermal bands were used to identify ice patterns and temperature differences in the surface water, which are indicative of ground-water discharge. Defining a shoreline specific to each image was critical in order to eliminate areas of the bays that were not representative of open water. Atmospheric correction was not necessary due to low humidity conditions during image acquisition. Ground-water discharge locations were identified on the north shore of Rehoboth Bay (west of the Lewes and Rehoboth Canal), Herring and Guinea creeks, the north shore of Indian River, and the north shore of Indian River Bay near Oak Orchard.