Predictions of future hydrological conditions and contribution of snow and ice melt in total discharge of Shigar River Basin in Central Karakoram,Pakistan

The high mountains of Hindu-Kush Karakoram and Himalaya(HKKH) contain a large volume of snow and ice, which are the primary sources of water for the entire mountainous population of HKKH. Thus, knowledge of these available resources is very important in relation to their sustainable use. A Modified Positive Degree Day Model was used to simulate daily discharge with the contribution of snow and ice melt from the Shigar River Basin, Central Karakoram, Pakistan. The basin covers an area of 6,921 km2 with an elevation range of 2,204 to 8,611 m a.s.l.. Forty percent of the total area is glaciated among which 20% is covered by debris and remaining 80% by clean ice and permanent snow. To simulate daily discharge, the entire basin was divided into 26 altitude belts. Remotely sensed land cover types are derived by classifying Landsat images of 2009. Daily temperature and precipitation from Skardu meteorological station is used to calibrate the glacio-hydrological model as an input variable after correlating data with the Shigar station data(r=0.88). Local temperature lapse rate of 0.0075 °C/m is used. 2 °C critical temperature is used to separate rain and snow from precipitation. The model is calibrated for 1988~1991 and validated for 1992~1997. The model shows a good Nash-Sutcliffe efficiency and volume difference in calibration(0.86% and 0.90%) and validation(0.78% and 6.85%). Contribution of snow and ice melt in discharge is 32.37% in calibration period and 33.01% is validation period. The model is also used to predict future hydrological regime up to 2099 by using CORDEX South Asia RCM considering RCP4.5 and RCP8.5 climate scenarios.Predicted future snow and ice melt contributions in both RCP4.5 and RCP8.5 are 36% and 37%, respectively. Temperature seems to be more sensitive as compared to other input variables, which is why the contribution of snow and ice in discharge varies significantly throughout the whole century.

Hydro-Chemical Characterization of Glacial Melt Waters Draining from Langtang Valley, Nepal

A detailed analytical study of the physico-chemical parameters of melt water draining from glaciers of Langtang Valley with an elevation ranging from 1395 m a s l to 4200 m a s l in Rasuwa district, Nepal was carried out in order to study the seasonal and altitudinal variation in hydro-chemistry along the Langtang River and glacial melts from the Lirung and the Khimsung Glaciers. The study was carried out during 6 - 10 April and 30 June-3 July, 2014 at 11 sites. A total of 22 composite samples were collected. The concentration of cations and anions of the Langtang Valley were found in the order Ca2+ > K+ > Na+ > Mg2+ and , respectively. Significant seasonal variation in electrical conductivity (EC), turbidity, dissolved oxygen (DO), calcium (Ca), sodium (Na), magnesium (Mg), chloride (Cl), sulphate (SO4) and total phosphorus (TP-PO4) and altitudinal variation in EC, total dissolved solids (TDS), DO and Na was found out. The concentrations of the heavy metals (As, Al, Mn, Zn, Cd, Cr) were below the detection limit except Fe (0.5 to 18.1 mg/l), which was highly variable. Calcium carbonate weathering was found out to be the major source of dissolved ions in the region. The elemental ratios (Ca/Si and K/Na) were typical of glacial melt water and the low Na/Cl and K/Cl ratios indicated major contribution from atmospheric precipitation to the observed dissolved ions of melt waters. The study showed an increase in the concentration of cations as compared to previous studies, which could be attributed to increasing weathering rates due to temperature increase. Elevated concentration of NO3 and TP-PO4 compared to previous studies show the effect of human impact in the region. Differences in the melt water composition between the debris covered and clean type glacier was found out.

Assessment of Sediment Load of Langtang River in Rasuwa District, Nepal

This paper assesses the sediment load of the glacier fed Langtang River, Nepal from April 2014 to March 2015. Water samples were collected from the centre of the river with a frequency of two samples per each sampling day using the Depth Integration Technique (DIT) on daily basis in the monsoon season, weekly in the pre- and post-monsoon seasons and bi-monthly in the winter season. Suspended sediment concentration (SSC) is calculated from the water samples using filtration followed by oven-drying, and a rating curve is used to calculate daily discharge of the Langtang River. The annual sediment yield is 109,276.75 tons and 37.69, 11.52 and 5.54 tons of sediment is transported per day in the pre-monsoon, post-monsoon and winter seasons, respectively. There is a very high value of 872.86 tons per day in the monsoon season, which contributes the highest sediment load among all of the seasons comprising 83% of the total sediment transport. Diurnal cycle of sediment discharge is clearly seen with higher sediment discharge during the evening than the morning and reaching maximum values of 41.1 kg·s-1 and 61.5 kg·s-1, respectively. A clock-wise hysteresis loop has been obtained for discharge and sediment discharge where sediment flux is higher in the early monsoon than in the late monsoon for a corresponding discharge.