Lab 9: Remote Sensing of Water Resources

Due Date: April 13, 2004

Objectives

·         To understand and identify considerations when remote sensing water resources.

·         Become familiar with several practical remote sensing water resource applications.

Remote sensing and GIS technologies offer a wide range of applications suitable for water resource investigation. Among these, the capability of discriminating among different land cover types using aircraft and satellite imagery is one of the most important. Cover classes may be identified for their significance to processes such as runoff yield, interception, and evapotranspiration. This type of information is useful for modeling basin-wide components of the water budget. Basin and channel features influence runoff and sedimentation in a watershed. GIS spatial analytic techniques can quantify such characteristics as slope, aspect, channel length, and drainage density. Low-altitude aerial photographs can be used to monitor changes in channel geometry over time.

Remote sensing and GIS are also useful for groundwater investigations. On a regional level, satellite imagery can be examined to define watershed boundaries, fracture zones, drainage patterns, and other features of hydrogeologic significance. Stereo viewing of large-scale aerial photography for relief and vegetation patterns, in conjunction with ground-referencing techniques, can provide valuable insights for localized studies. In some cases, airborne imagery can be used to locate seeps and springs.

Evaluating Impacts of Hurricane Floyd

Hurricane Floyd churned the coastal waterways of North Carolina like a spoon in a mixing bowl. Following Floyd, record breaking rains continued to soak the area, washing mountains of sediment and waste into the water system. Rivers and tributaries along the Atlantic became choked, and major ecological changes happened as evidenced in the SeaWifs images below. Levels of dissolved oxygen in the water dropped dramatically as organic matter decomposed, and aquatic life was threatened in dozens of estuaries and peripheral habitats. For people living in the region, the flood that began with Floyd was just the beginning. As illustrated in the following images, the changes to the area since this rainy season began affected hundreds of thousands of people.

From space, Landsat 7 captured the massive flow of sedimentation and waste runoff in the area most affected by flooding. Notice the dark coloration in the engorged waterways, indicating heavy concentrations of organic material that was washed into the water system.

Courtesy of NASA's Scientific Visualization Studio.

ASSIGNMENT

1. After a careful analysis of the above imagery, describe how remote sensing technology can be used as a tool to assess Hurricane Floyd's effect on algae blooms and phytoplankton, important links in the regional marine food chain, and how it could help to understand how the hurricane's aftermath might affect the fragile environment in the months after the event.

2. As a remote sensing specialist, choose one of the five scenarios listed below and write a discussion on the appropriate sensor systems to be used, suitable bands, identification of necessary biophysical variables, special considerations in remote sensing of water resources, and any other factors you would investigate (such as ancillary data integration). Be sure to include logic and examples from the text.

a. Estimating Snow Pack in California

You are recruited by the State of California to develop a new model using remote sensing technology that will predict future water supplies for the state. Satellite observations of surfaces blanketed by snow are often used to measure the areal extent of the masses likely to melt and track seasonal variation in snow cover from year to year. The State of California wants you to set up a cooperative snow survey project that involves estimating water supply conditions throughout California in the form of snowpack conditions and watershed runoff forecasts.

b. Preserving Water Quality in Florida Bay

You have been hired by the Florida Department of Environmental Protection as a remote sensing specialist to help restore water quality and improve marine habitat in the Florida Bay, an estuary ecosystem that comprises nearly 1000 square miles between the Florida Everglades and the Florida Keys. This estuary provides nursery habitat for immense numbers of fish species and other marine life that are fundamental to Florida's Tourism industry as well as the many ecosystems that extend beyond Florida Bay. In recent years adverse changes in Florida Bay have been observed. These changes include seagrass and sponge dieoffs, fish and crustacean population decreases, and a decline in water quality.

c. Long-Term Monitoring of Caribbean Coral Reefs

You are to produce the first comprehensive set of digital maps of coral reefs for the Caribbean Sea. Less than 10 percent of all coral reefs have been adequately mapped and characterized to determine their current condition. It is important to develop a coral reef map so these areas can be protected. The maps will create an accurate baseline for long-term monitoring, illustrate trends in reef health over time, characterize habitats and enhance scientific understanding of large-scale oceanographic and ecological processes affecting reefs.

d. Flood Management on the Mississippi

FEMA is hiring you to investigate new models and methods to reduce the impacts and dangers of flooding on the Mississippi River using remote sensing technology. Spring flooding is frequent in parts of the Mississippi River basin where a hundred-year flood, (i.e., largest expected statistically in a 100-yr span) can occur on a less than twenty year cycle. Excessive rain can saturates the soil, break levees, inundate tens of thousands of acres, and cause up to $15 billion in damage as it did in the 1993 flood.

e. Fighting Hyacinth on Lake Victoria

A recent unexpected discovery has uncovered a source of nutrients that has allowed a water weed to grow out of control in Africa's Lake Victoria and is putting a stranglehold on the lake's environment. You have been commissioned by the Kenya-based International Center for Research to use satellite technology to detect plumes of nitrogen- and phosphorous-rich sediments that are feeding the water hyacinth, a floating weed that starves fish and plankton of oxygen and sunlight. The hyacinth also blocks waterway traffic, causing water in the lake to stagnate. This makes the shoreline a breeding ground for mosquitoes that spread malaria and snails that are a host of bilharzia, a human parasite that attacks the liver, lungs and eyes. Hyacinth grows around the edge of the lake and creates a snake-like web of roots in the water. It impedes fishing boats from going out and is choking the commerce that occurs around the lake.

3. The integration of remote sensing and GIS with water quality models is becoming increasingly important as urban areas continue to expand. Models can be developed which predict surface-sampled water quality parameters such as turbidity, chlorophyll-a concentration, and surface temperature from digital image data. Thermal band imagery is extremely useful in creating the river and lake temperature maps that are necessary for some environmental and biological related projects. Images acquired from both airborne and spaceborne sensors are used for this purpose. These models can then be applied to water covered areas in the image, enabling generation of surface water quality maps. What information might be derived from such models that a water resource manager would benefit from?