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Spatially explicit, near real time information on surface water dynamics is critical for understanding changes in water resources, and for long-term water security planning. The distribution of surface water across the African continent since 1984 and updated as every new Landsat scene becomes available is presented here, and validated for the continent for the first time. We applied the Water Observations from Space (WOfS) algorithm, developed and well-tested in Australia, to every Landsat scene acquired over Africa since the mid 1980s to provide spatial information on surface water dynamics over the past 30+ years. We assessed the accuracy of WOfS using aerial and satellite imagery. Four regional geospatial organisations, coordinated through the Digital Earth Africa Product Development Task Team, conducted the validation campaign and provided both the regional expertise and experience required for a continental-scale validation effort. We assessed whether the point was wet, dry, or cloud covered, for each of the 12 months in 2018, resulting in 34,800 labelled observations. As waterbodies larger than 100 km2 are easy to identify with Landsat resolution data and can thus boost accuracy, these were masked out. The resulting overall accuracy of the water classification was 82%. WOfS in Africa is expected to be used by ministries and departments of agriculture and water across the continent, by international organisations, academia, and the private sector. A large-scale collaborative effort, which included regional and technical skills spanning two continents was required to create a service that is regionally accurate and is both hosted on, and implemented operationally from, the African continent.

In recent decades, severe climate change, decreased precipitation, temperature rise, and increased evapotranspiration (ET) have significantly reduced waterbodies. Furthermore, governments have prioritized the study of water level fluctuations of lakes to protect them from degradation nationally and regionally. The present study investigated the physical changes in lakes Bakhtegan and Tashk due to climatic parameters. To this end, Landsat satellite imagery and the NDWI were employed to calculate the area of the waterbodies from 1986 to 2018. The results showed that the area had decreased during the study period-- since 2009, Lake Bakhtegan had dried up completely. In 2008 and 2010, the lowest precipitation was 127.82 and 107.7 mm, respectively. During the study period (1986 to 2018), the average temperature was 19.44 °C, with an increase of 0.6 °C. Among the climatic parameters, precipitation, with a correlation coefficient of 0.55, and potential evapotranspiration (PET), with a correlation coefficient of about −0.68, were more strongly correlated with changes in the area of the waterbodies. To predict temperature and precipitation in the study area in the coming decades (2020–2050), the HadCM2 model of the CORDEX Project -WAS (South Asia) was used under two scenarios: RCP4.5 and RCP8.5. These scenarios revealed the decrease in precipitation and increase in temperature trends. As a result, the waterbodies’ areas were estimated using the projected precipitation and PET for the period 2050–2020, indicating a decrease in the areas of the waterbodies.

In addition to religious content layers, the word hiis (holy grove) seems to express also certain features of a natural landscape. The article discusses the issues concerned with the location of hiis areas as well as their meaning. There are signs of links between ‘holy’ and ‘hiis’ that can be traced in the toponymy observed in both lore and maps, although it is not always that place lore or placenames have survived in written form until today. The main emphasis in the article is placed on the water element related to holy groves, waterbodies and springs as well as wetlands. Often the holy grove is situated at a watershed or headspring, next to springs, the mouth of a river or a stream, a (former) larger waterbody or karst area. Water connects many places, and holy places can often be found in the marginal areas or junctions of waterbodies. In the case of water and presumably also holy places, place lore seems to consider as essential the ability to move in different ways and change the shape – this is reflected, for example, in legends about travelling nature objects as indicators of holiness. On occasion, the hiis areas mark natural reservoirs of clean groundwater; this is essential to acknowledge as the issue of water still occupies a crucial role among other environmental problems. So the stereotype of hiis as a holy grove, so-called Taara oak grove, embodies remarkably broader possibilities for interpreting the holiness of places in today’s context, for valuing these places and protecting them both culturally and environmentally.

Nitrate (NO3−) pollution of surface and groundwater bodies is a global problem of increasing concern, which has stimulated significant research interest. Nitrogen is crucial for life as a macronutrient for living organisms on Earth, but the global nitrogen cycle has been seriously altered by intensification of human activities, leading to eutrophication and hypoxic conditions of aquatic ecosystems. Due to nitrogen overfertilization, intensive agricultural practices generate huge nitrate fluxes that inadvertently deteriorate water quality. Different industrial processes also contribute to NO3− pollution in the environment. There are multiple technologies capable of achieving effective denitrification of waterbodies to ensure safe NO3− levels. Either separation-based or transformation-based denitrification technologies must address the challenges of by-product generation, increased energy demand, and reduced environmental footprint. This paper highlights the most used approaches, along with some promising alternatives for remediation of nitrate-polluted waters.

This work reported the development, prototyping and validation of a low-cost colorimetric paper-based sensor for the analysis of phenolic contaminants in waterbodies. The device was constructed using chromatographic paper and the chromogenic probe was Folin Ciocalteu reagent. Results evidenced that undiluted chromogen solution and 15% sodium carbonate allowed the maximum performance of the sensor, which exhibited adequate linearity between 100 mg l−1 and 1000 mg l−1 and limits of detection and quantification of 25 and 1000 mg l−1, respectively for the phenolic probes herein used (e.g. gallic acid, catechol, pyrogallol and vanillin), as well as adequate recovery for gallic acid upon recovery test. Moreover, the paper-based sensor was used to evaluate a real sample, and results were compared to a standard test, thereby presenting no statistically significant difference (i.e. 505.21 mg l−1 for the standard test and 517.49 mg l−1 for the paper-based sensor, p > 0.05). The findings therefore suggests that the biosensor herein described is a low-cost and valuable alternative to detect and quantify phenolic contaminants in waterbodies.

Anthropogenic activities causing a transformation of the natural nitrogen and phosphorus cycle are considered as one of the most fundamental environmental issues. In this study, nitrate and phosphate concentrations in waterbodies such as Abadaba river, Agulu lake, Njaba river, Oguta Lake, and Nike Lake located in Southeast, Nigeria was determined in both dry and wet season by spectrophotometric technique and modeled for pollution and health risks assessment. Result revealed that nitrate ranged from 13.163±2.30 mg/L at Nike to 36.173±7.22 mg/L Oguta lake in dry season while in the wet season it ranged from 17.402±3.459 mg/L at Abadaba to 26.748±6.536 mg/L at Njaba river. Phosphate ranged from 2.144±0.513 mg/L at Nike to 9.741±3.207 mg/L at Oguta in dry season while from 36.330±7.420 mg/L at Abadaba to 40.204±6.024 mg/L at Oguta. Comparing results with World Health Organization (WHO) allowed limits, it revealed that nitrate was low while phosphate was only low in the dry season at Abadaba, Agulu and Oguta lake. The waterbodies showed low variations (< 20 %) with positive linear relationships (R2 ≥ 0.3) for both nitrate and phosphate in both dry and wet season. Furthermore, except at Abadaba and Agulu in the dry/wet season and Njaba and Oguta in wet season, which showed no significant differences (p > 0.05) between them, all other showed significant difference (p < 0.05) for nitrate and phosphate concentrations. In terms of season, only at Njaba (for phosphate only) showed no significant differences (p > 0.05), all others waterbodies showed significant differences (p < 0.05) in nitrate and phosphate concentration in both seasons. The nitrate to phosphate ratio was very low especially in the wet season due to the high input of phosphate. The nutrient pollution index showed moderate to very high pollution while the waterbodies will pose very high non-carcinogenic health risks to users via the oral pathway. Overall, the waterbodies are at risk of eutrophication and efforts should be put in place to reduce anthropogenic activities around the area and thus input of nutrients in these water bodies.

The Tatun Volcanic Group (TVG), located in northern Taiwan, is characterized by acidic hot springs where the outflow of the hot springs may affect the properties of the associated lotic water bodies. We investigated the bacterial diversity and functional profiles of the Peihuang (PHC), HuangGang (HGC), and Nanhuang Creeks (NHC) located in the TVG basin using 16S rRNA gene sequencing coupled with statistical analyses. Water samples were collected from various streams of the creeks for two months of the year. The NHC showed the highest diversity, richness, and a unique number of phyla, which was followed by the HGC. A reduced number of phyla and a lower diversity was noticed in the PHC. The NHC was found to be abundant in the genera Armatimonas, Prosthecobacter, Pirellula, and Bdellovibrio, whereas the HGC was rich in Thiomonas, Acidiphilium, Prevotella, Acidocella, Acidithiobacillus, and Metallibacterium. The PHC was abundant in Thiomonsa, Legionella, Acidocella, and Sulfuriferula. The samples did not show any strong seasonal variations with the bacterial diversity and abundance; however, the relative abundance of each sampling site varied within the sampling months. The iron transport protein- and the sulfur metabolism-related pathways were predicted to be the key functions in all the creeks, whereas the heavy metal-related functions, such as the cobalt/nickel transport protein and the cobalt–zinc–cadmium efflux system were found to be abundant in the HGC and PHC, respectively. The abundance of Bdellovibrio in the NHC, Diplorickettsia in the HGC, and Legionella in the PHC samples indicated a higher anthropogenic impact over the creek water quality. This study provides the data to understand the distinct bacterial community structure, as well as the functional potentials of the three major watersheds, and helps the knowledge of the impact of the physicochemical properties of the TVG hot springs upon the watersheds.

The study of phytoperiphyton communities in waterbodies and watercourses typical for the State Nature Reserve «Kivach» (Republic of Karelia, Russia) included the analysis of their taxonomy composition, ecology and space distribution such as abundance. In total, 156 species were identified from different substrates, belonging to Cyanophyta (Cyanoprokaryota) (21), Ochrophyta (96), Dinophyta (2), Euglenophyta (2), Chlorophyta (35). The paper has discussed the main principles of structure formation of phytoperiphyton communities in rivers. Based on the analysis of taxonomic composition and structure of attached algal communities the similarity features in community composition were revealed. The lists of species dominating in terms of abundance and biomass differ appreciably. Phytoperiphyton communities, dominated by typical attached forms such as Tabellaria flocculosa, Eunotia pectinalis Cocconeis placentula, and Achnanthes minutissima were most common and abundant. However, the bulk of biomass was formed mainly by the filamentous green algae Cladophora glomerata, Mougeotia sp., Zygnema sp., and Bulbochaete sp. We indicated that ecological-geographical composition of algae is dominated by widespread oligohalobic species being acidophilic or indifferent to medium pH. According to the assessments, water in lakes and one brook belonged to the oligosaprobic type and class II of water purity. Periphyton abundance and biomass in waterbodies studied ranging from 0.1 × 104 cell cm-2 to 1301.1 × 104 cell cm-2 and 0.01 mg/cm-2 to 34.70 mg/cm-2.

Changes in land use and land cover (LULC) are the leading contributors to the decline and loss of ecosystem services in the world. The present study covered the Central Rift Valley lakes basin in Ethiopia, focusing on the valley floor and the East and West escarpments, to analyze changes in LULC and to estimate associated losses in ecosystem service values (ESVs). Covering both upstream and downstream areas in the basin, the study addressed major gaps in existing studies by connecting the sources and sinks of material (e.g., sediment and water) in source-to-lake systems. Additionally, the study facilitated the identification of critical areas for conserving natural resources and reversing the decline of associated ESVs in the Central Rift Valley. A post-classification comparison approach was used to detect LULC changes between 1973 and 2020 using four Landsat images from 1973, 1990, 2005 and 2020. The value transfer valuation method was used to estimate the changes in ESVs due to LULC changes. Among the seven major identified LULC classes, farmlands, settlements, and bare lands showed positive changes, while forestlands, grasslands, shrublands and waterbodies showed negative changes over the last 47 years. The expansion of farmlands, for example, has occurred at the expense of grasslands, forestlands and shrublands. The changes in LULC over a period of 47 years resulted in a total loss of US $62,110.4 × 106 in ESVs. The contributors to the overall loss of ESVs in decreasing order are provisioning services (US $33,795.1 × 106), cultural services (US $28,981.5 × 106) and regulating services (US $652.9 × 106). The results imply that addressing the degradation of land and water resources is crucial to reversing the loss of ecosystem services and achieving the national Sustainable Development Goals (SDGs) related to food and water security (SDGs 2 and 6) and life on land (SDG 15).

Arctic lowlands are characterized by large numbers of small waterbodies, which are known to affect surface energy budgets and the global carbon cycle. Statistical analysis of their size distributions has been hindered by the shortage of observations at sufficiently high spatial resolutions. This situation has now changed with the high-resolution (

Water detection algorithms are now being routinely applied to continental and global archives of satellite imagery. However, water resource management decisions typically take place at the waterbody rather than pixel scale. Here, we present a workflow for generating polygons of persistent waterbodies from Landsat observations, enabling improved monitoring and management of water assets across Australia. We use Digital Earth Australia’s (DEA) Water Observations from Space (WOfS) product, which provides a water classified output for every available Landsat scene, to determine the spatial locations and extents of waterbodies across Australia. We generated a polygon set of waterbodies that identified 295,906 waterbodies ranging in size from 3125 m2 to 4820 km2. Each polygon was used to generate a time series of WOfS, providing a history of the change in surface area of each waterbody every ~16 days since 1987. We demonstrate the applications of this new dataset, DEA Waterbodies, to understanding local through to national-scale surface water spatio-temporal dynamics. DEA Waterbodies provides new insights into Australia’s water availability and enables the monitoring of important landscape features such as lakes and dams, improving our ability to use earth observation data to make meaningful decisions.