Impact of Glacial Reduction and Change in the Water Environment on a Local Community on Mt. Kenya

Abstract

Glaciers on Mt. Kenya have been shrinking rapidly during recent decades due mainly to global climate change. In the south-facing upper watershed on Mt. Kenya, the water supply is insufficient for the farmland and daily lives of the inhabitants because of the shortage of water available from both the Naromoru River and precipitation, with large interannual and seasonal fluctuations. No observational field research has been conducted to determine the contribution of glacial meltwater to the water environment in this watershed. Thus, the present study aimed to elucidate the current conditions of the water environment in the upper part of the Mt. Kenya watershed through hydrogeochemical field observations and interviews with local residents.

The range of δ18O values of the spring at the foot of Mt. Kenya (ca. 2,000m) was -4.12‰ to -3.33‰, and δD values ranged from -20.66‰ to -15.91‰. In addition, δ18O values of the Naromoru River water (ca.2,000m) ranged from -3.29‰ to -2.85‰, and δD values from -13.42‰ to -7.58‰. Both of these values were similar to those of the glacier icemelt water (δ18O=-4.35‰ to -1.88‰, δD=-27.44‰ to -9.83‰). We also calculated the high altitude effect and thus estimated the altitude of water sources for the spring and river which are utilized at the foot of the mountain. That is, by substituting the average δ18O value of the river water (-3.03‰; range 1,858‒2,090m) into the high-altitude effect line (E [m]=-380.96*δ18O +3496.4), the source altitude was estimated to be 4,650m. On the other hand, the source altitude for the spring water (altitude: 1,943‒2,089m) was estimated to be 4,718m. These results suggest that the glacier and snowfall on the higher elevations contribute greatly to the Naromoru River and spring at the foot of Mt. Kenya.

In addition, tritium and chlorofluorocarbon (CFC) levels in water samples indicated that it takes groundwater 40‒60 years to emerge at the foot of Mt. Kenya after initially penetrating the glacial area at an altitude of approximately 5,000m. Hence, the present reduction in the glacier size on Mt. Kenya suggests that the water volume in the area around the foot of the mountain will decline in the near future.