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- Title
An Isotope Mass Balance Analysis of Evaporative Loss From Lake Turkana, Kenya Using δ<sup>18</sup>O and δD of Natural Waters.
- Authors
Saslaw, M.; Yang, D.; Lee, D.; Poulsen, C. J.; Henkes, G. A.
- Abstract
Measurements of oxygen and hydrogen stable isotope ratios (δ18O and δD) in meteoric waters provide insight to overlapping effects of evaporation, precipitation, and mixing on basin scale hydrology. This study of waters collected between 2016 and 2021 in the Turkana Basin, northern Kenya, uses δ18O and δD to understand water balance in Lake Turkana, a large, low‐latitude, alkaline desert lake. The Omo River, a major river system in the Ethiopian Highlands, is historically understood to provide approximately 90% of the water input to Lake Turkana. Discharge of the Omo is prohibitively difficult to measure, but stable isotope ratios in the lake may provide a meaningful method for monitoring the lake's response to changes in input. Precipitation in the Turkana Basin is low (<200 mm/year) with negligible rainfall on the lake's surface, and all water loss from the lake is evaporative. We compare new measurements with previous data from the region and records of lake height and precipitation from the same time period. We show that a Bayesian approach to modeling evaporation using atmospheric conditions and river δ18O and δD yields results consistent with published water balance models. Continued sampling of lake and meteoric waters in the Turkana Basin will be a useful way to monitor the lake's response to regional and global climate change. Plain Language Summary: Lake Turkana is the largest desert lake in the world, in one of the hottest and driest places on Earth. Studying and preserving the lake are important because people and ecosystems depend on it, but information is lacking because it is remote and irregularly monitored. Most of the water in Lake Turkana comes from the Omo River, which flows through the Ethiopian Highlands. Lake Turkana has no outlet; therefore, evaporation is the only process that removes water from the lake. In this study, we analyzed samples of lake water as well as rain, river, surface, and ground waters and developed a model that uses measurements of oxygen and hydrogen stable isotopes in the water to help us understand how much evaporation occurs in Lake Turkana. Future lake water monitoring efforts should consider stable isotope methods to record how the basin hydrology responds to climate change. Key Points: New measurements of meteoric waters from the Turkana Basin in northern Kenya plot along the meteoric water lineA lake water evaporation line is developed using Bayesian modeling applied to a terminal lake mass balance modelThe model enables predictions of lake water δ values under past and future climate change scenarios
- Subjects
KENYA; OXYGEN isotopes; ENDORHEIC lakes; GROUNDWATER; CLIMATE change; HYDROGEN isotopes; LAKES; MASS budget (Geophysics)
- Publication
Water Resources Research, 2024, Vol 60, Issue 6, p1
- ISSN
0043-1397
- Publication type
Article
- DOI
10.1029/2023WR036076