Water pollution characteristics of inflowing rivers under different land-use patterns in the Daye Lake basin: pollution mode and management suggestions

Land use/land cover (LULC) conditions can have a profound impact on the water quality of rivers, lakes, and other water bodies within a basin. Land use status of Daye Lake basin in 2019 has been shown by Landsat 8 OLI image, water quality of Daye Lake, and 12 inflowing rivers have been investigated once a month; this study provides a comprehensive analysis of the water pollution characteristics of the inflowing rivers and lake in the basin under different LULC patterns, and providing a reference for the scientific planning of land-use types in the basin and land use research in lake basins in subtropical areas. Pollutants are mainly introduced to Daye Lake from the west (such as Da Gang) and north (such as Linjiaju Gang), with concentrations gradually decreasing within the lake from west to east. Construction land is closely associated with the total nitrogen (TN), total phosphorus (TP), permanganate index (COD_Mn), and ammonia nitrogen (NH₃-N) inputs to the basin, which can be trapped by vegetation. Agricultural dryland can contribute acid and dissolved oxygen (DO) to water. Precipitation can influence the input of pollutants, with a stronger effect on TN and weaker effect on TP. Pollutants accumulate from the inlets to the centre of the lake, with longer retention times during the dry season.

Seasonal evaluation of downscaled land surface temperature: A case study in a humid tropical city

The present study evaluates the seasonal variation of estimated error in downscaled land surface temperatures (LST) over a heterogeneous urban land. Thermal sharpening (TsHARP) downscaling algorithm has been used with a separate combination of four selected remote sensing indices. This study assesses the capability of TsHARP technique over mixed land use/land covers (LULC) by analyzing the correlation between LST and remote sensing indices, namely, normalized difference built-up index (NDBI), normalized difference vegetation index (NDVI), normalized difference water index (NDWI), and normalized multi-band drought index (NMDI) and by determining the root mean square error (RMSE) and mean error (ME) produced by downscaled LST. Landsat 8 OLI (Operational Land Imager) and TIRS (Thermal Infrared Sensor) images have been used for pre-monsoon, monsoon, post-monsoon, and winter seasons in 2014 covering the whole Raipur City, India. The RMSE of the downscaled LST decreases from 120 to 480 m spatial resolution in all the four seasons. It is concluded that NDBI is the most effective LULC index having the least error produced in TsHARP downscaling technique, irrespective of any season. Post-monsoon season reflects the most successful result followed by monsoon season. Even in the monsoon season of high vegetation coverage, NDBI presents a lower range of downscaled error compared to NDVI. This indicates better performance of NDBI in detecting the spatial and temporal distribution of mixed urban land.

Assessment of land use/land cover dynamics of Tso Moriri Lake, a Ramsar site in India

Wetlands accounts for 6% area of the Earth's land cover and nearly 17% of the Hindu Kush Himalayan region. They are of utmost importance to climate dynamics and are critical links between terrestrial and aquatic ecosystems. Despite the need of high attention towards conserving and managing wetland resources, mapping them is a least practiced activity. This study shows the temporal change in land use and land cover pattern of Tso Moriri Lake, the highest altitude lake in India and designated as Ramsar site in year 2002, using multi-sensor and multi-date imagery. Due to change in hydro-meteorological conditions of the region, this lake area has been reduced. Since the lake recharge is dependent on snowmelt, hence change in climatic conditions (less snowfall in winters), to a certain extent, is also responsible for the decrease in water level and water spread of the lake. The result shows that the lake area has reduced approximately 2 km² in the last 15 years, and also, agriculture, grasslands, and vegetation cover have increased to a significant extent. Agricultural land and grasslands have doubled while the vegetation cover has increased more than six times, showing the coupled effect of climate change and anthropogenic activities. Trend of temperature and precipitation corroborates the effects of climate change in this region.