Since the lunch of Landsat in 1972, a human has “eyes” from space. Satellite observations by NOAA AVHRR series enable to monitor vegetation activities over the globe. Here the author takes an overview in remarkably achieved the Earth observation satellites or sensors for hydrological sciences and global water cycle studies, such as 1) optical sensor of MODIS boarded on Terra and Aqua platforms, 2) AMSR series microwave passive imager, 3) TRMM PR and GPM DPR precipitation radars, 4) GRACE: gravity observation mission and 5) the 3rd generation geostationary meteorological satellites, such as Himawari-8, GOES-R series.

To elucidate the characteristics of the water quality of Lake Issyk-Kul, wherein the water level is rising but salinity is increasing as well, and those of the river and spring waters in its basin, a survey was conducted in the summers of 2012–2014. Based on the analysis results for the main chemical components and the dissolved organic carbon (DOC), the present conditions of the water quality characteristics of the river and spring water and the change in the salinity condensation of the lake are summarized. The chemical composition of the river and spring water is mostly Ca–HCO₃ type; however, the river and spring water passing through urban areas and farmland contain many anthropogenic Na⁺, Cl⁻, SO₄²⁻, NO₃⁻, and DOC components. The water composition of the lake is NaCl, SO₄ type, and the condensation rate of each component can be divided into three groups of Na+, Cl⁻, Mg²⁺, SO₄²⁻, Ca²⁺, and HCO³⁻. As for the water quality of the lake as of 2014, the Na⁺, Mg²+, Cl⁻, and SO₄²⁻ concentrations have continued to increase since 1986 and the increase in the Cl⁻ concentration has been remarkable in recent years. The majority of the river water quality of the Lake Issyk-Kul catchment area consists of naturally-derived elements; however, in some river and spring waters, anthropogenic Na⁺, Cl⁻, and SO₄²⁻ are introduced and the inflow of these components is one of the causes of the current increased salinity of Lake Issyk-Kul.

This study focused on the concentration of the sulfide ion, which causes corrosion of a heat exchanger that exchanges heat with a buried steel pipe and pumped groundwater. The research target was shallow groundwater at 10 m depth or less located in the town of Fujisaki, Aomori Prefecture. Surveys were conducted almost monthly for one year from July 2017 to June 2018. The study results show that the sulfide ion concentration in the groundwater reached 0.6 µmol/dm³ twice, in February and March of 2018. The fluctuation of sulfide ion concentration was not clearly related to the concentration of chemical species involved in the sulfate reduction reaction and to the concentration of chemical species involved in other redox reactions.