Hydrological and ecological impacts of run off river scheme; a case study of Ghazi Barotha hydropower project on Indus River, Pakistan.

Run off river schemes are getting widespread importance as they are considered environmentally safe. However, number of studies and the consequent information regarding impacts of run off river schemes is very limited worldwide. Present study attempted to analyze impacts of Ghazi Barotha Hydropower Plant, which is a run off river scheme situated in Khyber Pakhtunkhwa province of Pakistan. This study attempted to analyze impacts of this run off river scheme on hydrological and ecological conditions of downstream areas. Data on river discharge, groundwater levels, agriculture area, vegetation and bare soil was utilized for this study. All data sets between the year 1990 till 2020 were analyzed. Hydrological impacts were analyzed through secondary data analysis, whereas ecological impacts were studied through remote sensing technique. Statistical methods were applied to further draw conclusions between hydrological and ecological interrelationships. Results showed that after functioning of Ghazi Barotha, there was 47% and 91% reduction of river discharge, in summer and winter seasons respectively. Groundwater level dropped by 50%. Agriculture area reduced by 1.69% and 9.11% during summer and winter respectively, whereas land under bare soil increased. River water diversion was considered to be responsible for groundwater reduction, as strong correlation was found between both. Agriculture land recovery, in post Ghazi Barotha period, was premised at intense groundwater mining, as groundwater level and agriculture area were significantly related (p < 0.05). Governments' groundwater development schemes, and a shift into motorized groundwater mining were major factors behind further groundwater exploitation in study area. This study came to the conclusion that Ghazi Barotha Hydropower Plant had impacted flow regime of Indus River, as well as groundwater levels and land use of downstream area along the river. These effects were triggered by inappropriate compensatory measures and uncontrolled water resource exploitation.

Characterization and health risk assessment of arsenic in natural waters of the Indus River Basin, Pakistan.

The elevated concentrations of arsenic in natural water are one of the major environmental threats to human health. However, the existing characteristics, controlling mechanisms, and associated risks of arsenic in natural waters in the Indus River Basin (IRB), Pakistan, are yet to be unequivocally understood. In this study, a total of 203 samples of surface water (SW), shallow groundwater (SGW), and deep groundwater (DGW) were collected from the IRB to assess the geochemical characteristics of arsenic and its associated health risks, as all three kinds of waters are the main sources of drinking and domestic usage. The results revealed that the arsenic concentrations in the SW, SGW, and DGW were in the ranges of 1.1-26.45, 1.05-44.44, and 0.67-41.09 µg L-1, respectively. Furthermore, the predominance of As (V) (97 %) over As(III) (3 %) confirmed that the desorption of As in oxidizing environments with elevated pH and Eh is the controlling mechanism. The hazard quotient of 11-45 % and 20-60 % samples and cancer risk of 26-64 % and 26-68 % samples indicated high health risks for the adults and children, respectively, suggesting an immense need for appropriate measures of reducing natural water arsenic concentrations in IRB from the human health perspectives.

Hydrochemical appraisal and solute acquisitions in Seti River Basin, Central Himalaya, Nepal.

The chemical characterization and assessment of the water quality in the headwater areas of the Himalaya are necessary for securing the water in the future. This study aims to assess the hydrochemistry and water quality concerning drinking and irrigational uses in the Seti River Basin (SRB), Nepal. A total of 45 water samples were collected in 2016 from the SRB during pre-monsoon, monsoon, and post-monsoon seasons, and pH, EC, TDS, and DO were measured on-site, whereas Ca2+, Mg2+, K+, Na+, Cl-, SO42-, NO3-, and dissolved Si were analyzed in the laboratory. The results revealed mildly alkaline pH (8.40 ± 0.43) with the pattern of average ionic dominancy: Ca2+ > Mg2+ > Na+ > K+ and HCO3- > SO42- > Cl- > NO3- for cations and anions, respectively. Gibbs diagram implied that the lithogenic weathering mainly controlled the solute acquisition process, which was further confirmed by the Piper diagram, exhibiting Ca-HCO3 as the governing hydrochemical facies (91%). The average molar ratios were 0.88, 8.33, and 6.86 of (Ca2+ + Mg2+)/TZ+, (Ca2+ + Mg2+)/(Na+ + K+), and HCO3-/(Na+ + K+), respectively, which specified that the carbonate weathering largely controlled the solute acquisition processes with a minor contribution of silicates. The mass budget calculation also confirmed the dominance of carbonate weathering (72.0%, 78.9%, and 62.0% in Pre-Monsoon, Monsoon, and Post-Monsoon, respectively) and the high monsoon rainfall's dilution effect to anthropogenic input of cations. Principal component analysis and correlation matrix exhibited that the major sources of ions in the basin were geogenic with minor anthropic signatures. Furthermore, water quality in connection to drinking and irrigation uses revealed that the basin has mostly retained its natural water quality. This investigation suggests that regular monitoring and assessment are essential for maintaining the water quality and ecological integrity in the Himalayan river basins.

Meltwater hydrochemistry at four glacial catchments in the headwater of Indus River.

Glacier runoff shows significant change under global warming in the headwater region of the Indus River with great impact on its highly populated downstream area, but the hydrochemistry characteristics of meltwater and the changing mechanism remain unclear in this region. In this study, runoff water samples were collected during May and June, 2015, from four glacial catchments in the Upper Indus Basin to investigate general characteristics and daytime dynamics of meltwater runoff together with sediment and chemical contents. Results showed that glacier runoff in the studied area had an alkaline pH and much higher sediment yields than the local average of the non-glacier areas. The carbonate-dominated geological feature in the four catchments resulted in single chemical facies of Ca-HCO3. The dominant process determining the glacier runoff chemistry was rock-water interaction, with less soluble minerals and less intensive evaporate weathering in the Passu and Gulmit catchments than the B&B and Hinarchi catchments. Comparing the investigated catchments, the larger glacier with longer flow path exhibited higher runoff but lower melting rate, higher SSC resulting from higher erosive power of flow, and higher solute concentrations as a consequence of more intensive contact of meltwater with rock minerals along the longer flow path. For individual catchments, a negative correlation between TDS and flow rate (R2 = 0.26~0.53) and changing trends of ion ratios with flow rate demonstrated that under intensive melting conditions, rock-water interactions were reduced, resulting in dilution of solutes. Overall, the general chemical characteristics of the investigated glacier runoff indicated geological control, whereas individual glacier illustrated hydrological control on the daytime dynamics of glacier runoff chemistry. The presence of glacier terminal lake and agriculture land can significantly alter the hydrochemistry of downstream runoff.