Abstract
In-situ monitoring of lake water quality in synergy with satellite remote sensing represents the latest scientific trend in many water quality monitoring programs worldwide. This study investigated the suitability of the Operational Land Imager (OLI) instrument onboard the Landsat 8 satellite platform in accurately estimating key water quality parameters such as chlorophyll-a and nutrient concentrations. As a case study the largest freshwater body of Greece (Trichonis Lake) was used. Two Landsat 8 images covering the study site were acquired on 30 October 2013 and 30 August 2014 respectively. Near concurrent in-situ observations from two water sampling campaigns were also acquired from 22 stations across the lake under study. In-situ measurements (nutrients and chlorophyll-a concentrations) were statistically correlated with various spectral band combinations derived from the Landsat imagery of year 2014. Subsequently, the most statistically promising predictive models were applied to the satellite image of 2013 and validation was conducted using in-situ data of 2013 as reference. Results showed a relatively variable statistical relationship between the in-situ and reflectances (R logchl-a: 0.58, R NH4+: 0.26, R chl-a: 0.44). Correlation coefficient (R) values reported of up to 0.7 for ammonium concentrations and also up to 0.5 and up to 0.4 for chl-a concentration and chl-a concentrations respectively. These results represent a higher accuracy of Landsat 8 in comparison to its predecessors in the Landsat satellites series, as evidenced in the literature. Our findings suggest that Landsat 8 has a promising capability in estimating water quality components in an oligotrophic freshwater body characterized by a complete absence of any quantitative, temporal and spatial variance, as is the case of Trichonis lake. Yet, even with the presence of a lot of ground information as was the case in our study, a quantitatively accurate estimation of water quality constituents in coastal/inland waters remains a great challenge. The launch of sophisticated spaceborne sensing systems, such as that of Landsat 8, can assist in improving our ability to estimate freshwater lake properties from space.
Highlights
Lake water is an essential renewable resource for mankind and the environment; it plays a key role in the European and the global economy since it is exploited for civil, industrial and recreational purposes
Our findings suggest that Landsat 8 has a promising capability in estimating water quality components in an oligotrophic freshwater body characterized by a complete absence of any quantitative, temporal and spatial variance, as is the case of Trichonis lake
Our study explored the use of remote sensing technology and of Landsat 8 Operational Land Imager (OLI) sensor, to accurately quantify certain water quality parameters
Summary
Lake water is an essential renewable resource for mankind and the environment; it plays a key role in the European and the global economy since it is exploited for civil (e.g., drinking water supply, irrigation), industrial (e.g., processing and cooling, energy production, fishery) and recreational purposes. With the use of remote sensing technology, which is often combined with Geographical Information systems (GIS), water systems data can be analyzed and alternative management scenarios can be presented Such an outcome offers important assistance to decision makers and governmental institutions in effectively monitoring lake conditions, implementing recovery strategies, and addressing any other water issues [7]. The use of remote sensing, often in combination with in-situ and numerical modeling, has been demonstrated as being a strategic tool for assessing and monitoring lake waters quality This is because it allows frequent surveys over large areas providing data in a cost-effective way for a variety of studies which need multi-scale temporal analysis [1] in [6]. This is because it allows frequent surveys over large areas providing data in a cost-effective way for a variety of studies which need multi-scale temporal analysis [1] in [6]. this combination has been of high importance since the promotion of the European Commission Water Framework Directive (EC, 2000), with Member States establishing lake water quality assessment schemes, and setting Chl-a reference conditions for European lakes [8] in [9]
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