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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.
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Constraining the Modern Hydrological Balance of Bear Lake, Utah‐Idaho: Insights From Stable Isotopes (δ 18 O and δ 2 H)
Abstract Freshwater lakes are vital water resources, especially in the context of a changing climate. Supplementing existing hydrological methods to monitor lake levels may greatly improve resource management, particularly in drought‐prone regions. In this study, we performed dual‐isotope (δ18O and δ2H) calculations to model the hydrological balance of Bear Lake, Utah‐Idaho. The lake is a critical water resource and site for paleoclimate studies of the latest Pleistocene. Using the Craig‐Gordon isotopic mass balance model, we simultaneously constrained unknown fluxes, including groundwater discharge and particularly evaporation, which is typically under‐constrained due to inconsistencies across existing methods. Data from community databases and sampling campaigns in 2022 and 2023 were utilized to derive an evaporation rate of 2.18 × 108 m3/yr (±4.94 × 106 m3/yr, 1σ using δ18O; ±3.47 × 106 m3/yr, 1σ using δ2H) at a calculated relative humidity of 0.62 above the lake. Detailed analysis of the sensitivity of the model revealed that parameters related to atmospheric moisture, particularly humidity and its isotopic composition, significantly influence evaporation estimates. Using carbonate‐based isotope data, we leveraged this sensitivity to provide insights in the evaporation and humidity at Bear Lake during different time periods. This study shows the potential of using modern water isotopic composition to aid with interpreting carbonate‐based paleoclimate data sets and informing current and future water resource management practices.
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- PAR ID:
- 10650764
- Publisher / Repository:
- AGU
- Date Published:
- Journal Name:
- Water Resources Research
- Volume:
- 61
- Issue:
- 4
- ISSN:
- 0043-1397
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1029/2024WR038264
