Classification Of Water Bodies Research Articles

Less rain, more water in ponds: a remote sensing study of the dynamics of surface waters from 1950 to present in pastoral Sahel (Gourma region, Mali)

Abstract. Changes in the flooded area of ponds in the Gourma region from 1950 to present are studied by remote sensing, in the general context of the current multi-decennial Sahel drought. The seasonal and interannual variations of the areas covered by surface water are assessed using multi-date and multi-sensor satellite images (SPOT, FORMOSAT, LANDSAT-MSS, –TM, and -ETM, CORONA, and MODIS) and aerial photographs (IGN). Water body classification is adapted to each type of spectral resolution, with or without a middle-infrared band, and each spatial resolution, using linear unmixing for mixed pixels of MODIS data. The high-frequency MODIS data document the seasonal cycle of flooded areas, with an abrupt rise early in wet season and a progressive decrease in the dry season. They also provide a base to study the inter-annual variability of the flooded areas, with sharp contrasts between dry years such as 2004 (low and early maximal area) and wetter years such as 2001 and 2002 (respectively high and late maximal area).The highest flooded area reached annually greatly depends on the volume, intensity and timing of rain events. However, the overall reduction by 20% of annual rains during the last 40 years is concomitant with an apparently paradoxical large increase in the area of surface water, starting from the 1970's and accelerating in the mid 1980's. Spectacular for the two study cases of Agoufou and Ebang Mallam, for which time series covering the 1954 to present period exist, this increase is also diagnosed at the regional scale from LANDSAT data spanning 1972–2007. It reaches 108% between September 1975 and 2002 for 91 ponds identified in central Gourma. Ponds with turbid waters and no aquatic vegetation are mostly responsible for this increase, more pronounced in the centre and north of the study zone. Possible causes of the differential changes in flooded areas are discussed in relation with the specifics in topography, soil texture and vegetation cover over the watersheds that feed each of the ponds. Changes in rain pattern and in ponds sedimentation are ruled out, and the impact of changes in land use, limited in the area, is found secondary, as opposed to what has often been advocated for in southern Sahel. Instead, major responsibility is attributed to increased runoff triggered by the lasting impact of the 1970–1980's droughts on the vegetation and on the runoff system over the shallow soils prevailing over a third of the landscape.

Monitoramento físico-químico das águas do arroio Pampa em Novo Hamburgo (RS)

Watercourses that pass through heavily urbanized areas in their waters carry domestic sewage and industrial effluents. Brazilian environmental legislation determines the monitoring and classification of water bodies, with subsequent publication of results. But in most cases it actually does not occur. The Pampa stream with most of its territory in the municipality of Novo Hamburgo (RS, Brazil), passes very neighborhoods inhabited and has all the sewage of these areas drained by its waters. It is also a receiving body of industrial effluents. Despite its mouth is approximately 1.5 km from the point of abstraction of water for the consumption of more than 250,000 people, is typical example of this situation. This work monitored by one year the waters of the Pampa stream, and the waters of the Sinos river upstream from the mouth of the creek, with samples spaced approximately 45 days, seeking classification under CONAMA Resolution 357 and the influence of water the stream at the point of Pampa Rio dos Sinos where is the abstraction of water for the city of Novo Hamburgo. The determination of the parameters at the sampling points of the Pampa stream and the point located in the Sinos river upstream from the mouth of the creek, were performed by the Analytical Center of the University Center FEEVALE. The influence of the waters of the Pampa stream Sinos River at the point of capture of the Municipal Sanitation Company (COMUS) was performed using data from this company and the Foundation for Environmental Protection Henrique Luiz Roessler - RS (FEPAM), groups that monitor this point of withdrawal of water. The waters of the Pampa stream for some parameters showed similar characteristics to domestic wastewater occurring in some samples collected high levels of chromium and nickel. The relevant impact caused by the waters of the Pampa stream Rio dos Sinos is on domestic sewage. But the finding of significant levels of chromium and nickel determine preventive care and the influence of industrial effluents in the waters of the stream. The solution to the current dire state chemical and microbiological water of the stream Pampa necessarily entails the construction and operation of systems for domestic wastewater treatment, and an effective monitoring of industrial effluents. Key words: water quality, monitoring, Pampa Stream.

Caution is needed when applying Margalef diversity index

The use of diversity indices has increased due to the necessity of testing different methodologies to develop the ecological status classification of water bodies within the water framework directive implementation. The Margalef diversity index is one of the indices applied within these aims. Several software packages calculate various diversity indices. However, these packages do not give any warning that for the Margalef index the data must be organized as absolute numbers and not as a density data matrix. In data expressed as number of individuals per square meter, if the sample size is lower than a square meter this index is sub estimated. With other diversity indices commonly used in ecological evaluation it is indifferent to use density data or absolute numbers since these indices only consider relative proportions in their calculus.

Assessment of the ecological status of European surface waters: a work in progress

The ‘normative definitions’ of ecological water quality classes given by the Water Framework Directive (WFD) are narrative descriptions of the conditions present in water bodies of different qualities relative to reference conditions found in unimpacted sites. In order to fill these descriptions with a more solid content, the definitions have been a subject of intensive development of quantitative methodologies for ecological status assessment as well as for rules and criteria for setting of reference conditions and ecological status boundaries for classification of water bodies. In this article, we recall the basic principles of the WFD that sometimes have been overlooked and point out some gaps remained and problems arisen during the ongoing implementation of the directive. Defining type-specific reference conditions for water bodies and finding biological metrics that sensitively reflect only the anthropogenic deviations from those conditions are the biggest challenges that the ecological status assessment faces. So far, there is no guarantee that reference conditions are comparable across EU Member States due to a lack of common criteria, which need still to be elaborated. Defining site-specific reference conditions instead of type specific is a novel approach that allows for minimizing uncertainties introduced by applying broad types. Search for new metrics has led to a real boom of multimetric indices which ought to be the adequate tool to measure the multiple human impairments but which should pass a thorough check before being included in monitoring programs. Curiously, some biological indices constructed as surrogates for chemistry (especially nutrients) start ‘living their own life’ and continue indicating the disturbance when the controlling factors change. This shows the obvious advantage of biological indicators against chemical ones. New challenges to WFD implementation are brought about by the need to consider the effects of alien species and climate change in the assessment framework, and by the nonlinear dose—response relationships dominating in biological systems. Attempts to diminish uncertainties in quality assessment have become a new labour-intensive field for researchers.

Definition of Wetland Typology for Hydro-morphological Elements Within the WFD. A Case Study from Southern Spain

The European Water Framework Directive (WFD) constitutes a new view of water resources management and provides a challenge in the development of new and accurate methodologies for the classification of water bodies. It is necessary to improve and develop approaches based upon scientific knowledge in order to achieve requirements of comparability throughout European waters. This contribution focuses on the development of a classification typology for a series of wetlands in southern Spain, based on hydromorphological elements. Spanish wetlands and playa-lakes are usually small (<50 ha) and temporary and, for that reason, only indirectly addressed in the WFD with respect to the status of ground water dependent ecosystems. The WFD does not provide any guidance on how to react to significant pressures and impacts on such ecosystems. In order to manage, protect and, if necessary, restore this type of water bodies, it is important to classify them according to the main factors involved in their hydrological functioning. The water balance of the playa-lakes has proved to be a valuable tool to determine the hydrological regime in a semi-arid climate. Surface-groundwater relationships are key elements in determining the water balance, but there are other elements that could indicate or corroborate the hydrological functioning of a playa-lake, such as hydro-chemical markers or morphometric indexes. The present work could constitute the basis for a discussion document for other regions and countries throughout Europe and elsewhere.

Classification of Water Bodies of Urban Territories in terms of Phytoplankton Diversity

Classification of Water Bodies of Urban Territories in terms of Phytoplankton Diversity

GROUPWISE MODELING STUDY OF BACTERIALLY IMPAIRED WATERSHEDS IN TEXAS: CLUSTERING ANALYSIS

ABSTRACT: Under the Clean Water Act (CWA) program, the Texas Commission on Environmental Quality (TCEQ) listed 110 stream segments in the year 2000 with pathogenic bacteria impairment. A study was conducted to evaluate the probable sources of pollution and characterize the watersheds associated with these impaired water bodies. The primary aim of the study was to group the water bodies into clusters having similar watershed characteristics and to examine the possibility of studying them as a group by choosing models for total maximum daily load (TMDL) development based on their characteristics. This approach will help to identify possible sources and determine appropriate models and hence reduce the number of required TMDL studies. This in turn will help in reducing the effort required to restore the health of the impaired water bodies in Texas. The main characteristics considered for the classification of water bodies were land use distribution within the watershed, density of stream network, average distance of land of a particular use to the closest stream, household population, density of on-site sewage facilities (OSSFs), bacterial loading from different types of farm animals and wildlife, and average climatic conditions. The climatic data and observed instream fecal coliform bacteria concentrations were analyzed to evaluate seasonal variability of instream water quality. The grouping of water bodies was carried out using the multivariate statistical techniques of factor analysis/principal component analysis, cluster analysis, and discriminant analysis. The multivariate statistical analysis resulted in six clusters of water bodies. The main factors that differentiated the clusters were found to be bacterial contribution from farm animals and wildlife, density of OSSFs, density of households connected to public sewers, and land use distribution.

Using historical data, expert judgement and multivariate analysis in assessing reference conditions and benthic ecological status, according to the European Water Framework Directive

The European Water Framework Directive (WFD) establishes a framework for the protection and improvement of estuarine and coastal waters, trying to achieve ‘good surface water status at the latest 15 years after the date of entry into force of this Directive’. One of the biological elements that should be analysed is the benthos and, as such, the WFD normative definitions describe the aspects of the benthic communities that must be included in the ecological status assessment of a water body. Therefore, it is essential to include, in the assessment, the different metrics that address those parameters identified in the normative definitions for each of the ecological status classes. In this contribution the use of the AMBI, richness and diversity, combined with the use, in a further development, of factor analysis together with discriminant analysis, is presented as an objective tool (named here M-AMBI) in assessing ecological quality status. This assessment requires previous classification of water bodies and typologies, together with the definition of reference conditions; this is undertaken in this contribution using historical data, expert judgement and multivariate analysis. The study has been undertaken by examining changes in benthic communities in the Basque Country, over the last decade, as a case-study, to demonstrate the accuracy and potential of these methodologies.

Phytoplankton as an Indicator of the Water Quality of the Deep Lakes South of the Alps

This paper offers a synoptic account of studies on the phytoplankton communities in the deep southern subalpine lakes (DSL) Garda, Iseo, Como, Lugano and Maggiore. The main cause of the degradation of the water quality in the DSL is eutrophication. The euphotic layers of these lakes are trophically different, ranging from the oligo-mesotrophy of lakes Maggiore and Garda to the meso-eutrophy of lakes Iseo and Lugano. The trophic status as estimated by using total phosphorus and chlorophyll a has provided consistent results in agreement with the models proposed by OECD (1982. Eutrophication of Waters. Monitoring, Assessment and Control, OECD, Paris). Though related with chlorophyll a and TP, the Secchi disk depths have significantly underestimated the trophic status of the DSL. Two trophic indices using the algal orders (PTIorders) and species (PTIspecies) were drawn up on the basis of the distribution of phytoplankton along a trophic gradient defined by the application of multivariate methods; the scores emerging from these indices were used to make a definitive ecological classification of water bodies on a scale from 1 to 5, in accordance with the Water Framework Directive. A third index (PTIOE) was computed as the ratio between the annual mean values of the cumulative biovolumes of two groups of algal orders with opposite trophic characteristics. The three PTI indices were highly correlated, providing a consistent classification of the water bodies. The indices proposed in this work were specifically adopted for use in the DSL. However, the criteria for their implementation constitute a robust and impartial tool for assessing similar indices in other lake typologies and for evaluating the degree of specificity of the trophic indicator values assigned to the single phytoplankton orders and species.

Macrophyte-based assessment of lakes - a contribution to the implementation of the European Water Framework Directive in Germany

The European Water Framework Directive requires ecological status classification and monitoring of surface and ground water bodies using biological indicators. To fulfill the demands of the Directive, a macrophyte-based assessment system was developed for application on four lake site types in Germany. Biological lake site types were established using differences in characteristic macrophyte communities, reflecting ecoregion, Ca2+ content, mixis and morphology. Ecological status classification of lake sites is based on macrophyte abundance along 275 transects in 95 natural German lakes and the calculation of a reference index value, in some cases supplemented by submerged vegetation data. The reference index quantifies the deviation of species composition and abundance from reference conditions and classifies sites to one of the five ecological quality classes specified in the Directive. Based on an example of Lake Chiemsee, Germany, the possibilities for a wholelake assessment are discussed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Establishing the ecological quality status of soft-bottom mining-impacted coastal water bodies in the scope of the Water Framework Directive

The aim of the present study was to check the usefulness of the benthic biotic indices proposed for application in the European water framework directive (WFD 2000/60/EC) for the ecological quality classification of coastal water bodies, together with some other benthic methodologies used in different countries of the world. The different approaches were applied in two marine ecosystems affected by the same heavy metal contamination source, coastal waters off Portmán and the Mar Menor coastal lagoon, both in SE Spain. Two marine biotic indices proposed for application in the Directive (AMBI and BENTIX) were used, together with community descriptors (abundance, Shannon–Wiener diversity, Margalef’s species richness, Pielou’s evenness and Simpson’s Dominance), the relative benthic index (RBI) and the abundance-biomass comparison method (ABC). Water-sediment interface toxicity bioassays using sea urchin embryos and sediment metal analysis served to check the classifications obtained. The classical community descriptors pointed to a progressive variation in benthic communities along the metal contamination gradient of Portmán, but, they did not correctly characterize the environmental status of the lagoon stations. Although the RBI was the index that best classified the sites according to their degree of pollution, the selection of indicator species can bias the results. Since the AMBI, the BENTIX and the ABC method are based on the pollution resulting from organic enrichment, their application in the case of purely toxic pollution may not be successful, as was found to be the case in these two mining-polluted ecosystems. Therefore, the development of new indicator lists according to the type of pollutant may serve to improve the results obtained with organic enrichment-based indices when studying other kinds of disturbance. Finally, we found the toxicity tests to be useful tools for the environmental assessment of aquatic ecosystems, and recommend their inclusion in the WFD.

Quantitative review of riparian buffer width guidelines from Canada and the United States

This paper reviewed the provincial, territorial, and state guidelines for the retention of treed riparian buffers after timber harvest in Canada and the United States. Comparisons amongst jurisdictions were facilitated through the use of a standardized template for the classification of waterbodies. Mean buffer widths varied from 15.1 to 29.0 m for different waterbody types when both countries were combined. However, Canadian jurisdictions had wider buffers (except for intermittent streams). In part, this was due to the high percentage of Boreal jurisdictions in Canada and Southeast jurisdictions in the United States. The Boreal region had the widest buffers while Southeastern jurisdictions had the narrowest buffers. Just under half (∼44%) of the jurisdictions investigated had three or more modifying factors in the guidelines. Of these, waterbody type, shoreline slope, waterbody size, and presence of fish were the most common. Boreal and Pacific jurisdictions tended to have a more diverse set of waterbody size classes, waterbody types, and other modifying factors. Jurisdictions from the Midwest, Northeast, and Southeast maintained relatively simple ‘one-size-fits-all’ guidelines. Jurisdictions without modifying factors for slope or presence of fish applied wider baseline buffers than jurisdictions with these factors. A large percentage of jurisdictions (∼80%) allowed some selective harvest in buffers. However, these were often accompanied by relatively restrictive prescriptions. In comparison to the ecological recommendations, buffer widths for most jurisdictions were adequate to protect the aquatic biota and habitats but were, generally, less than recommended widths for terrestrial communities. In the future, two management trends are likely to continue, the shift towards more complicated guidelines and the expansion to larger-scale, watershed planning of riparian areas.

Combining biological indicators of watershed condition from multiple sampling programs—a case study from Maryland, USA

Abstract Freshwater biological monitoring and assessment programs using biological indicators of ecological integrity (biocriteria) are integral to successful water resources planning and decision making. In the United States, the Clean Water Act requires every state to evaluate whether or not the designated aquatic life use (defined in its water quality standards) is being attained for each river and stream, and to submit a biennial list of impaired waters for US Environmental Protection Agency (EPA) approval. Economic constraints (personnel, equipment, transportation, laboratory, and data management costs) on water quality monitoring present a considerable challenge to states in reaching this goal. Many US states are using biocriteria-based statewide monitoring of the condition of surface waters to meet this challenge. The sampling effort of state monitoring programs, however, is often not sufficient to provide reliable estimates of stream condition for individual watersheds. Fortunately, other organizations such as county and municipal governments, regional water management authorities, and volunteer watershed groups are also gathering valuable stream monitoring data. When more than one monitoring program is conducted in a local watershed, it is desirable to integrate the estimates to (1) provide consistent estimates of stream condition, (2) increase the effective sample size and hence precision of the estimates, and (3) improve the spatial coverage of the stream network. In this paper, we show how a composite estimator can be used to combine the results of more than one probability-based survey to estimate mean condition in watersheds. As an example, we estimate the mean Fish Index of Biotic Integrity (IBI) for the Seneca Creek watershed in the State of Maryland, combining estimates from the Maryland Biological Stream Survey (MBSS) and the Montgomery County Stream Monitoring Program. Separate estimates are provided for the network of streams that are in the sample frame of both surveys and for the expanded stream network covered only by the Montgomery County survey. The composite estimate of mean Fish IBI for the streams common to both programs has a lower standard error than the MBSS estimate and yields a consistent estimate of stream condition that can be used to evaluate Seneca Creek watershed for inclusion in the State’s priority list of impaired waters. For the expanded stream network, the composite estimation also increased the precision of the mean Fish IBI relative to the Montgomery County estimate. The combination of surveys across space result in increased precision because of increased sample sizes and the application of weights that minimize the variance, and hence can provide more definitive classification of water bodies and reduce the need for follow-up monitoring. Integration of survey estimates can improve communication with the public and ultimately lead to more reliable water resource management decisions. State, provincial, and regional authorities in the US and other countries can use the composite indicator estimation technique presented here to derive more information from their limited monitoring resources and make better water resource protection decisions.

Remote sensing of riverine landscapes

1. The fashion for examining riverine landscapes is changing as our technical instruments, from microprobes to satellites, expands to be able to examine the spatial and temporal relationships among biota, hydrology and geomorphology across scales from microhabitats to channel units to valleys to catchments.2. The range of successful applications from remote sensing analyses of riverine landscapes has especially increased with the launch of many new instruments that record data across the electromagnetic spectrum. Engineering of the instruments has also improved such that knowledge of the radiometric properties of the digital data is more complete as a result of better instrumentation and installation of on‐board calibrations systems for many instruments.3. With the development of faster processing on cheaper computers, it is now common for comprehensive data sets to be processed through algorithms that previously could only be applied to relatively small (&lt;1 Mbyte) rasters of data. This technical advance is especially important for the statistical algorithms such as principal components and spectral mixture analysis that can decompose gradients in the spectral data. The combined effect is the production of regional views of riverine landscapes separated into components of water, vegetation and soil.4. The landscape properties of riverine landscapes that have been most successfully measured with remote sensing data include community and habitat level classification and connectivity of waterbodies with optical and radar data. Laser and radar altimetric data measured from aircraft provide land elevations at resolutions as fine as decimetres. A remaining challenge is to achieve an exact match between the categories of landscape classification from the remote sensing analysis and data from field surveys or model outputs.5. In contrast to many landscape properties, several water properties are now routinely measured as absolute values (water surface elevation, temperature, surface sediment concentration and algal concentration) with remote sensing. New analyses of both passive and active radar data in addition have led to measurements of inundation and wetness that are providing valuable insight into the dynamics of flooding and its effect on riverine landscapes.6. Finally, an effective examination of the variability in landscape cover includes additional analyses of remote sensing products using pattern metrics that measure the scale of patchiness and distribution of the landscape properties. These types of variability measures at the regional scale contribute to an increased understanding of the way in which spatial heterogeneity of riverine landscapes varies across scales and how landscape filters (sensu Poff, 1997) influence the evolution of these diversity patterns.

On the Method of Numerical Taxonomy as Applied to Classification of Water Bodies

Method of numerical taxonomy is analyzed in the context of its application to zoning and classification of water areas.

15. 水環境指標動物としてのユスリカ類(第56回日本衛生動物学会西日本支部大会講演要旨)

15. 水環境指標動物としてのユスリカ類(第56回日本衛生動物学会西日本支部大会講演要旨)

Apples, oranges, and ecoregions: on determining pattern in aquatic assemblages

Classification of waterbodies is a necessary step for aquatic biological assessment. Geographic classes, such as physiographic provinces, marine biogeographic provinces, and ecoregions are frequently used as a classification framework for conducting bioassessments. An alternative to such a priori classification of waterbodies is to let the biological data tell us, using various statistical exploratory techniques to identify classes that do not necessarily conform to geographic stratification. In assessment of new sites, it is often necessary to identify or predict which of several classes the new site may belong to. We classified benthic macroinvertebrate assemblages from streams of Wyoming, using 3 alternative methods: a priori establishment of ecoregions, adaptive modification of the ecoregions, and a posteriori clustering. Classification strengths were compared using similarity dendrograms. Clustering separated the sites better than ecoregions, but the clusters showed strong ecoregional affinities. The modified ecoregions were equal to the clusters in classification strength. We conclude that an iterative process that includes generation of hypotheses, exploratory data analysis, and evaluation and modification of hypotheses is most likely to produce robust classifications, regardless of specific analytical approaches used.

Application of remote sensing and geographic information systems to the delineation and analysis of riparian buffer zones

Non-point source pollution has a significant impact on the quality of water resources. Studies have revealed that agricultural activities are often major contributors to non-point source pollution of aquatic environments. A common means of reducing the threat of non-point source pollution is through the establishment of riparian vegetation strips (or buffers) along those areas of stream channels that would be most susceptible to the threat. Remote sensing and geographic information systems (GIS) offer a means by which ‘critical’ areas can be identified, so that subsequent action toward the establishment of riparian zones can be taken. This research focuses on the development and analysis of riparian buffer zones for a portion of the Iowa River basin. Landsat Thematic Mapper (TM) data were used to characterize the land cover for the study area. An updated hydrology data layer was developed by integrating the United States Geological Survey (USGS) Digital Line Graph (DLG) data base with the TM-derived classification of surface water bodies. Spatial distance search tools were applied to develop the buffer zones around all surface hydrologic features. The buffer zones were integrated with the remotely sensed classification data to identify ‘critical’ areas for the establishment of riparian vegetation strips. Results indicated that while most of the main channel of the Iowa River was protected by natural vegetation, more than 44% (or 1008 ha) of the area along its tributaries lack any protective cover from non-point source pollution. As these ‘critical’ areas are adjacent to agricultural fields it is important that water resources management strategies focus on the establishment of riparian zones in order to minimize the impact of non-point source pollution.

Optical classification of waters in the eastern arabian sea

The optical properties in a non-spectral mode covering Photosynthetically Active Radiation (PAR) was estimated in the Arabian Sea in the west coast of India. The attenuation coefficients, light transmittance and K/c ratio were found useful for classification of water bodies in the coastal and offshore region. High values of turbidity and Chlorophyll-a in coastal waters associated with comparatively higher values of diffusive attenuation coefficients for upwelling and downwelling irradiances. On the basis of attenuation coefficients and K/c ratio derived from upwelling and downwelling irradiances, the water bodies were classified as defincd by Jerlov (1976). The coastal waters are classified under Jerlov water types of 3 to 9, whereas those of offshore are falling under the categories Ia, Ib and II.

The spatio-temporal patterns and ecological significance of free amino acids and humic substances in contrasting oligotrophic and eutrophic freshwater ecosystems

The concentrations of total and individual free amino-acids (TFAA, FAA) and humic substances (HS) were measured by HPLC in the midwater column (MWC), air-water interface (AWI) and sediment pore water (SPW) in the oligotrophic, dystrophic Isle of Thorns lake and the eutrophic Lewes Brooks drainage channel in East Sussex, UK, during each of the four seasons. Pesticide levels were low, usually below detection levels in both water bodies. At the temporal level there were tendencies for the concentration of both FAA and HS to be lowest in the winter months and for the HS concentrations to be higher in the autumn in both water bodies. At the spatial level the eutrophic Lewes Brooks was characterized by having much higher FAA/HS ratios than the oligotrophic Isle of Thorns lake and it is suggested that further comparative studies be undertaken to verify whether the FAA/HS ratios may have general application in the classification of water bodies on a trophic basis. The concentrations of TFAA are higher in the SPW and AWI than in the MWC in both water bodies and the HS concentrations are much higher in the SPW than in the MCW Statistical analyses support the view that the FAA in the MWC are mainly derived from the SPW whereas the FAA in the AWI have a different origin. The data obtained is used to address the following questions: (a) How do the spatio-temporal patterns of FAA and HS in the present study areas compare with those of other water bodies? (b) What are the origins of the FAA and HS and how are their concentrations regulated? (c) Are the distributional patterns of FAA and HS of special significance to invertebrate detritivores? (d) How can the differences in the FAA and HS patterns in oligotrophic and eutrophic waters be explained? What are the conclusions and testable hypotheses arising from the present study?