Inland Water Monitoring Research Articles

Global inland water monitoring from multi‐mission altimetry

By “illuminating” the Earth's inland water surfaces with radar altimeter data from the ERS‐1 Geodetic Mission, a global waveform analysis has shown that over 50% of echoes from even the largest lake targets are non‐ocean‐like in character. This paper shows that by retracking multi‐mission altimeter data, height data can be obtained from the vast majority of lakes with surface area greater than 500 km2. Results from the Amazon Basin also show the great improvement in both quantity and quality of data obtained. These results graphically demonstrate that by retracking all available echoes over inland water, the potential of altimetry to measure and monitor global land surface hydrology can be realized.

Construction of a Prototype Database System for Water Temperature in Japan and the Surrounding Sea

An attempt was made to construct a prototype database system for water temperature using geographical information such as the attributes of monitoring points in Japan and the surrounding sea, and World Databank II. First, we collected sample data on temperature and information such as the location, attributes and observation systems of stations for monitoring of inland water and seawater temperature through questionnaires in Japan. Secondly, datafiles for the attributes and factual data were constructed. Finally the retrieval system was developed using parameters such as the locality number of each point, the latitude and longitude of the point, frequency of data sampling, method of temperature sensing, kind of sensor, sensor depth, media for raw data and the frequncy of data recording.

Measurement of river level variations with satellite altimetry

Quantitative assessment of water levels and river discharge is often made difficult by large distances, limited access, and low population densities in remote areas. Satellite altimetry provides a repetitive remote sensing approach to determining river levels at a number of locations within a river system, providing the orbital repeat cycle is short enough in time, the ground track maintains a stable repeat over previous locations, and the return power of the altimeter signal can be readily identified and located. The U.S. Navy's Geosat radar altimeter mission between 1985 and 1989 provided the first altimeter measurements with sufficient precision and extended duration to examine the utility of such measurements for long‐term monitoring of inland waters. These measurements have been examined over the Amazon basin. Satellite observations are retrieved at four locations that overlap with river gauge measurements. A technique is developed to isolate radar return signals from the river. Two years of satellite measurements are compared with the river gauge retrievals. The overall level of comparison is 0.7 m rms when the technique is applied manually, and 1.2 m rms when an automated version of the method is applied. At one location the average difference is 0.2 m rms. This level of accuracy may not be useful for routine hydrological measurements. However, there are a variety of difficulties that are specific to the Geosat altimeter measurement over rough terrain. Present altimeter satellites, ERS 1 (launched June 1991) and TOPEX/Poseidon (launched August 1992), correct many of these problems. This study suggests that the prospect for obtaining useful measurements of river level from space is promising.

Using NOAA AVHRR imagery in assessing water quality parameters

Abstract The Advanced Very High Resolution Radiometer (AVHRR) instrument, carried by the NOAA-TIROS/N series of operational meteorological satellites can, on a routine basis, provide observational data which allow interpretation in terms of parameters related to water quality. In principle, some, though not all of the algorithms applied to Coastal Zone Colour Scanner data can be transformed for use with AVHRR observations. In combination with the operational character of the NOAA satellites this opens up the way to applications in monitoring of open sea and inland waters. Algorithms and results for some examples of such potential applications are presented.

THE APPLICATION OF PHOSPHORUS LOAD - TROPHIC RESPONSE RELATIONSHIPS TO RESERVOIRS

Analysis of the data obtained in the UECD Cooperative Program on Monitoring of Inland Waters (Eutrophication Control) (126 bodies of water) revealed that data from several reservoirs do not fit the Vollenweider type nutrient load-nutrient concentration and trophic response, empirical relationships. These outliers were long or narrow reservoirs where the intake concentration of total phosphorus was estimated based on measurements near the outflow, thus it was not representative for the whole body of water. This misrepresentation of the average intake concentration may be corrected if the reservoir is treated as a series of connecting individual bodies of water where each segment would fit the empirical phosphorus loading relationships.