Digital Signal Processing Reference
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water, or reducing inlet water by allowing flexible water levels, can also be modelled. Dahl et al.,
2006, developed a combined suspended particle and phosphorus water quality model was developed
and applied on Lake Vänern in Sweden . The model was modified to handle two separate sub-basins,
but increasing the horizontal resolution further by splitting the basins into coastal area and pelagial
failed, as the model fit to experimental data deteriorated. Besides, the scant reference data available for
the coastal areas makes this a dubious exercise. Parameters for the nutrient dynamics in the water
column required less tuning (up to 60%) than the sedimentation and sediments (up to a factor 70). The
fit to experimental data is good for the periods between 1900 and 1940 and that after 1980, but is less
satisfactory for the more polluted conditions in the middle of the century. The model is applied to two
scenarios: increased emissions from a pulp and paper mill by the lake, and decreased phosphorus
emissions achieved by a combination of effects on farmland, woodland, and rural households. These
two scenarios demonstrate the usefulness of a dynamic quantitative lake water quality model.
Zacharias
and
Gianni, (2008) studied the water circulation inside the re-flooded Drana lagoon using a
hydrodynamic model. Several cases were investigated based on different driving forces, such as tide,
wind and fresh water inflows. And also the study dealt with an advection/dispersion model that was
used for the spatial and temporal simulation of both temperature and salinity. Oceanographical and
meteorological field measurements were used for the calibration and validation of both models. The
computed daily water temperature variations were well correlated with the data gained during the field
observations.
3.4.
A
PPLICATIONS OF REMOTE SENSING IN SURFACE WATER QUALITY MODELLING
3.4.1.
Overview of Data Supporting Water Quality Remote Sensing
The traditional measurement of water quality requires in situ sampling, which is a costly and time-
consuming effort. Because of these limitations, it is impractical to cover the whole water body or
obtain frequent repeat sampling at a site. This difficulty in achieving successive water quality
sampling becomes a barrier to water quality monitoring and forecasting (Senay et al. 2001). It would
be advantageous to watershed managers to be able to detect, maintain and improve water quality
conditions at multiple river and lake sites without being dependent on field measurements (Shafique el
al., 2002). Remote sensing techniques has the potential to overcome these limitations by providing an
alternative means of studying and monitoring specific water quality parameters such as total
suspended matter and CHL-aorophylla over a wide range of both temporal and spatial scales.
Several studies have confirmed that remote sensing can meet the demand for the large sample sizes
required for water quality studies conducted on the watershed scale (Senay el al., 2001). Hence, it is
not surprising that a significant amount of research has been conducted to develop remote sensing
methods and indices that can aid in obtaining reliable estimates of these important hydrological
variables. These methods ranged from semi-empirical techniques to analytical methods for estimating
and producing quantitative water quality maps. Several researchers have developed regression
formulas to predict several lake water quality parameters from satellite data by employing spectral
ratios or indices. These water quality parameters have included CHL-aorophyll a concentration,
suspended matter concentration and turbidity.
Lately, a few studies have used remote sensing data collected from different platforms, such as
ground-based, airborne, and satellite for mapping and monitoring of water quality. This section
reviews the literature particularly how ground based; airborne and satellite-based remote sensing data
were used in the mapping and monitoring of water quality.
Ground-Based Data Collection
Traditionally, ground-based collection of water-quality data is done using field samples or field
spectrometers. Field samples are collected by hand at many geographically specific locations in the
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