Periodic Reporting for period 1 - HydrO-17 (Improving water management in semi-arid regions: Insights in hydrological and environmental controls of lakes using triple oxygen isotopes)
Periodo di rendicontazione: 2022-10-01 al 2024-09-30
Water is essential for life, the economy, and climate regulation, yet its scarcity is intensifying due to population growth, urbanization, and economic development. Water shortages are particularly remarkable in arid and semi-arid areas like the Mediterranean, where low rainfall and high evaporation severely limit water availability.
This is especially pronounced in arid and semi-arid regions like the Mediterranean, where low rainfall and high evaporation severely limit water availability. Southern Spain faces a serious water crisis due to decades of overexploitation of groundwater for agriculture, leading to a lower water table, saltwater intrusion in coastal aquifers, and ecosystem degradation, all of which are projected to worsen with climate change.
In this context, sustainable water management depends on a thorough understanding of hydrological systems and their responses to environmental changes. Lakes in semi-arid regions play a critical role as water resources for agriculture and industry and as wildlife habitats, yet little is known about their hydrological functioning, and quantitative approaches to evaluate their water balances and climate sensitivity are underutilized. The HydrO-17 project addresses this gap by using hydrochemical monitoring and innovative stable isotope geochemistry tools to study lake water balances and responses to climate change. Additionally, the project’s findings will support improved paleoclimate interpretations from sediment archives, informing water management strategies for long-term ecosystem health.
This is especially pronounced in arid and semi-arid regions like the Mediterranean, where low rainfall and high evaporation severely limit water availability. Southern Spain faces a serious water crisis due to decades of overexploitation of groundwater for agriculture, leading to a lower water table, saltwater intrusion in coastal aquifers, and ecosystem degradation, all of which are projected to worsen with climate change.
In this context, sustainable water management depends on a thorough understanding of hydrological systems and their responses to environmental changes. Lakes in semi-arid regions play a critical role as water resources for agriculture and industry and as wildlife habitats, yet little is known about their hydrological functioning, and quantitative approaches to evaluate their water balances and climate sensitivity are underutilized. The HydrO-17 project addresses this gap by using hydrochemical monitoring and innovative stable isotope geochemistry tools to study lake water balances and responses to climate change. Additionally, the project’s findings will support improved paleoclimate interpretations from sediment archives, informing water management strategies for long-term ecosystem health.
To assess the novel isotope tool's potential, we monitored the isotope evolution of four distinct lake systems. We collected 233 water samples, including lake water, precipitation, groundwater, vapor, and evaporation experiment samples, each analyzed for triple oxygen and hydrogen isotopes. Two lakes were equipped with instruments to monitor water levels and chemical parameters. Combined with isotope evaporation modeling, this real-time data allowed us to predict the isotope evolution of lake water over the year, providing essential insights into how these lake systems might respond to environmental changes in semi-arid regions.
To improve the interpretation of triple oxygen isotopes of lacustrine gypsum for quantitative paleoclimate reconstruction, we collected gyspum samples from the lake surface in one of the monitored lakes. By comparing the isotope composition of these gypsum samples with the seasonal isotope variation in lake water, we were able to identify the specific seasonal period recorded in the gypsum.
In addition, we collected and analysed 58 water samples from three artificial salt pans to better understand the effect of salinity on isotope fractionation during evaporation. This data was essential for refining our isotope evaporation model, enhancing its accuracy for lake systems with varying salinities.
To improve the interpretation of triple oxygen isotopes of lacustrine gypsum for quantitative paleoclimate reconstruction, we collected gyspum samples from the lake surface in one of the monitored lakes. By comparing the isotope composition of these gypsum samples with the seasonal isotope variation in lake water, we were able to identify the specific seasonal period recorded in the gypsum.
In addition, we collected and analysed 58 water samples from three artificial salt pans to better understand the effect of salinity on isotope fractionation during evaporation. This data was essential for refining our isotope evaporation model, enhancing its accuracy for lake systems with varying salinities.
Our findings identified that relative humidity as the main driver of isotope variability both in permanent and ephemeral lake systems in semiarid environements. We showed that the rate at which lake water responds to changing environmental conditions is strongly influenced by the proportion of water loss through evaporation relative to the lake’s volume. We also observed that inflow from precipitation and basin discharge is intermittent, leading to transitional mixing effects that further affect isotope compositions.
A key insight was that seasonal isotope variability provides a distinguishing marker between permanent and ephemeral lake systems. Notably, combining triple oxygen and hydrogen isotope measurements allows for the identification of ephemeral (non-steady state) conditions, which is critical for monitoring lakes that may respond quickly to seasonal changes.
We also found that gypsum forms in spring and early summer, prior to complete lake desiccation—an insight crucial for enhancing paleoclimate reconstructions from lake sediment records.
Additionally, we found that the effects of evaporation on the isotope composition of interconnected ponds can be more pronounced than expected for a single groundwater-recharged lake. Our analysis also showed that lake salinity significantly influences isotope fractionation during evaporation, as increased salinity alters solution density and reduces evaporation rates. These results underscore the need to account for salinity effects in isotope models.
A key insight was that seasonal isotope variability provides a distinguishing marker between permanent and ephemeral lake systems. Notably, combining triple oxygen and hydrogen isotope measurements allows for the identification of ephemeral (non-steady state) conditions, which is critical for monitoring lakes that may respond quickly to seasonal changes.
We also found that gypsum forms in spring and early summer, prior to complete lake desiccation—an insight crucial for enhancing paleoclimate reconstructions from lake sediment records.
Additionally, we found that the effects of evaporation on the isotope composition of interconnected ponds can be more pronounced than expected for a single groundwater-recharged lake. Our analysis also showed that lake salinity significantly influences isotope fractionation during evaporation, as increased salinity alters solution density and reduces evaporation rates. These results underscore the need to account for salinity effects in isotope models.