Spatial pattern of lake evaporation increases under global warming linked to regional hydroclimate change

Lakes are critical natural resources that are vulnerable to climate change. In a warmer climate, lake evaporation is projected to increase globally, but with substantial variation between regions. Here, based on ensemble projections of climate and lake models and an attribution method, we show that future lake evaporation increase is strongly modulated by regional hydroclimate change. Specifically, a drying hydroclimate will amplify evaporation increase by enlarging surface vapor pressure deficit and reducing cloud shortwave reflection. Future lake evaporation increase is amplified in tropical America, the Mediterranean and Southeast China with drier future hydroclimates, and dampened in high latitudes and the Tibetan Plateau with wetter future hydroclimates. Such spatially coupled changes in lake evaporation and hydroclimate have important implications on regional lake water balance and volume change, which can aggravate water scarcity and flood risks.

Stable isotopes in global lakes integrate catchment and climatic controls on evaporation

Global warming is considered a major threat to Earth’s lakes water budgets and quality. However, flow regulation, over-exploitation, lack of hydrological data, and disparate evaluation methods hamper comparative global estimates of lake vulnerability to evaporation. We have analyzed the stable isotope composition of 1257 global lakes and we find that most lakes depend on precipitation and groundwater recharge subsequently altered by catchment and lake evaporation processes. Isotope mass-balance modeling shows that ca. 20% of water inflow in global lakes is lost through evaporation and ca. 10% of lakes in arid and temperate zones experience extreme evaporative losses >40 % of the total inflow. Precipitation amount, limnicity, wind speed, relative humidity, and solar radiation are predominant controls on lake isotope composition and evaporation, regardless of the climatic zone. The promotion of systematic global isotopic monitoring of Earth’s lakes provides a direct and comparative approach to detect the impacts of climatic and catchment-scale changes on water-balance and evaporation trends.

Climate Change Impact On Lake Tana Water Storage, Upper Blue Nile Basin, Ethiopia

Temperature and precipitation trend fluctuations influence the components of the hydrological cycle and the availability of water supplies and their resulting shifts in the balance of lake water (lake level). Quantile mapping was applied to correct temperature biases, and power transformation was applied for rainfall correction. The performance of the HBV model was evaluated through calibration and validation using objective functions (RVE, NSE) and provide RVE of 3.7%, -1.27%,1.05%, -0.72%,8.9% and -0.68 during calibration and RVE of -1.5%, 6.93%, -3.04%,8.796%, -5.89% and 8.5 % during validation for Gumara, Kiltie, Koga, Gilgel Abay, Megech and Rib respectively, While the model provided NS of 0.79,0.63,0.72,0.803,0.68 and 0.797 during calibration and NSE of 0.8,0.64,0.7,0.82,0.801 and 0.82 during validation for Gumara, Kiltie, Koga, Gilgel Abay, Megech, and Rib respectively. The simulated Lake level showed adequate agreement to the observed with NS and RVE of 0.7 and 6.44 % respectively. The result confirmed that over lake evaporation and rainfall increase for all future scenarios. The ungauged surface inflow is also increased shortly scenarios while gauged surface inflow increased for RCP4.5 (the 2070s) and RCP8.5 (2040s) and decreased for RCP4.5 (2040s) and RCP8.5 (2070s). The decreased in gauged surface water inflow is due to a decrease in inflow for Gilgel Abay, Koga and Gumara gauged catchments. Lake storage results showed a decrease in all future scenarios of all-time horizons.

Re-discovering Robert E. Horton's Lake Evaporation Formulae: New Directions for Evaporation Physics

Evaporation from open water is among the most rigorously studied problems in hydrology. Robert E. Horton, unbeknownst to most investigators on the subject, studied it in great detail by conducting experiments and heuristically relating his observations to physical laws. His work furthered known theories of lake evaporation, but it appears that it got dismissed as simply empirical. This is unfortunate, because Horton’s century-old insights on the topic, which we summarize here, seem relevant for contemporary climate change-era problems. In re-discovering his overlooked lake evaporation works, in this paper we: 1) examine his several publications in the period 1915–1944 and identify his theory sources for evaporation physics among scientists of the late 1800s; 2) illustrate his lake evaporation formulae which require several equations, tables, thresholds, and conditions based on physical factors and assumptions; and 3) assess his evaporation results over continental U.S., and analyse the performance of his formula in a subarctic Canadian catchment by comparing it with five other calibrated (aerodynamic and mass transfer) evaporation formulae of varying complexity. We find that Horton’s method, due to its unique variable vapor pressure deficit (VVPD) term, outperforms all other methods by ~ 3–15 % of R2 consistently across timescales (days to months), and an order of magnitude higher at sub-daily scales (we assessed up to 30 mins). Surprisingly, when his method uses input vapor pressure disaggregated from reanalysis data, it still outperforms other methods which use local measurements. This indicates that the vapor pressure deficit (VPD) term currently used in all other evaporation methods is not as good an independent control for lake evaporation as Horton's VVPD. Therefore, Horton's evaporation formula is held to be a major improvement in lake evaporation theory which, in part, may: A) supplant or improve existing evaporation formulae including the aerodynamic part of the combination (Penman) method; B) point to new directions in lake evaporation physics as it leads to a "constant" and a non-dimensional ratio – the former is due to him, John Dalton (1802), and Gustav Schübler (1831), and the latter to him and Josef Stefan (1881); C) offer better insights behind the physics of the evaporation paradox (i.e. globally, decreasing trends in pan evaporation are unanimously observed, while the opposite is expected due to global warming). Curiously, his rare observations of convective vapor plumes from lakes may also help explain the mythical origins of Greek deity Venus and the dancing Nereids.

The Holocene lake-evaporation history of the afro-alpine Lake Garba Guracha in the Bale Mountains, Ethiopia, based on δ18O records of sugar biomarker and diatoms

In eastern Africa, there are few long, high-quality records of environmental change at high altitudes, inhibiting a broader understanding of regional climate change. We investigated a Holocene lacustrine sediment archive from Lake Garba Guracha, Bale Mountains, Ethiopia, (3,950 m asl), and reconstructed high-altitude lake evaporation history using δ18O records derived from the analysis of compound-specific sugar biomarkers and diatoms. The δ18Odiatom and δ18Ofuc records are clearly correlated and reveal similar ranges (7.9‰ and 7.1‰, respectively). The lowest δ18O values occurred between 10–7 cal ka BP and were followed by a continuous shift towards more positive δ18O values. Due to the aquatic origin of the sugar biomarker and similar trends of δ18Odiatom, we suggest that our lacustrine δ18Ofuc record reflects δ18Olake water. Therefore, without completely excluding the influence of the ‘amount-effect’ and the ‘source-effect’, we interpret our record to reflect primarily the precipitation-to-evaporation ratio (P/E). We conclude that precipitation increased at the beginning of the Holocene, leading to an overflowing lake between ca. 10 and ca. 8 cal ka BP, indicated by low δ18Olake water values, which are interpreted as reduced evaporative enrichment. This is followed by a continuous trend towards drier conditions, indicating at least a seasonally closed lake system.

Contrasting hydrological and thermal intensities determine seasonal lake-level variations – a case study at Paiku Co on the southern Tibetan Plateau

Evaporation from hydrologically closed lakes is one of the largest components of the lake water budget; however, its effects on seasonal lake-level variations remain unclear on the Tibetan Plateau (TP) due to a lack of comprehensive observations. In this study, weekly lake evaporation and its effects on seasonal lake-level variations are investigated at Paiku Co on the southern TP using in situ observations of thermal structure and hydrometeorology (2015–2018). Lake evaporation from Paiku Co was estimated to be 975±142 mm during the ice-free period (May to December), characterized by low values of 1.7 ± 0.6 mm d−1 during the pre-monsoon season (May to June), high values of 5.5±0.6 mm d−1 during the post-monsoon season (October to December), and intermediate values of 4.0±0.6 mm d−1 during the monsoon season (July to September). There was a ∼ 5-month lag between the maximum net radiation (June) and maximum lake evaporation (November). These results indicate that the seasonal pattern of lake evaporation from Paiku Co was significantly affected by the large lake heat storage. Contrasting hydrological and thermal intensities may play an important role in the large amplitude of seasonal lake-level variations at deep lakes like Paiku Co. High inflow from monsoon precipitation and glacier melting and moderate lake evaporation, for instance, drove rapid lake-level increase during the monsoon season. In contrast, high lake evaporation and reduced inflow caused lake level to decrease significantly during the post-monsoon season. This study implies that lake evaporation may play an important role in the different amplitudes of seasonal lake-level variations on the TP.

Multi-model projections of evaporation in a sub-tropical lake

<p>Evaporation of surface water is critical to the basic functioning of lakes. It directly and, in some cases, substantially modifies the hydrologic, chemical, and energy budgets, making evaporation one of the most important physical controls on lake ecosystems. Predicting lake evaporation response to climate change is, therefore, of paramount importance. Most studies that simulate climate change impacts on lake evaporation have utilised only a single mechanistic model. Whilst such studies have merit, the advantage of applying multiple, independently developed models (i.e., an ensemble approach), is that some of the inherent uncertainties in the individual lake models due to, for example, different model structures, can be reduced thus enabling increased robustness of historic and future projections. In this study, we present results from the Inter-Sectoral Impact Model Intercomparison Project phase 2b (ISIMIP) Lake Sector, where lake evaporation responses to 20<sup>th</sup> and 21<sup>st</sup> century (1901-2099) climate change has been simulated with a suite of independently developed lake models under different climate change scenarios (Representative Concentration Pathways, RCP, 2.6, 6.0 and 8.5). Our study focuses on Lake Kinneret (Israel), a sub-tropical monomictic lake of socioeconomic importance. Our simulations are validated during the historic period with bulk evaporation estimates calculated from high frequency meteorological and in-lake observations. Our results demonstrate that the lake models provide an accurate representation of historical variability in lake evaporation, with promising comparisons of the magnitude, timing and seasonality of evaporative water loss. Future evaporation projections at Lake Kinneret show that evaporation anomalies will increase by the end of the century. We show that multi-model projections of lake evaporation can accurately represent the historic period and hence provide reliable future projections that will be vital for water management.</p>

Holocene lake water-aquifer interactions in La Ballestera Playa-lake (southern Spain) recorded by stable isotopes (δ18O and δD) of gypsum hydration water

<p>Oxygen and hydrogen stable isotopes (δ<sup>18</sup>O and δD) of lake water are sensitive to long-term changes in environmental conditions, including relative humidity, temperature and the evaporation/outflow ratio of the lake. Lacustrine gypsum (CaSO<sub>4</sub>·2H<sub>2</sub>O) forms in equilibrium with its parent fluid, so the isotopic composition of its structurally bonded hydration water (GHW) can reflect the δ<sup>18</sup>O and δD of lake water at the time of mineral formation, with insignificant effects of temperature and salinity on the water-GHW isotope fractionation factors. Using the stable isotope content of gypsum-rich sediment cores as a paleoclimatic proxy, the environmental conditions prevailing in the lake setting at the time of gypsum crystallization can be investigated.</p><p>Here we apply this method to reconstruct the δ<sup>18</sup>O and δD of paleo-water in La Ballestera Playa-lake (Seville, southern Spain) throughout the Holocene, from 11.2 cal kyr BP to the present. Gypsum crystallization took place punctually at 11.2 and 4.4 cal kyr BP, and did continuously from 2.9 cal kyr BP to the present. The δ<sup>18</sup>O and δD showed the lowest values at ~11.2 cal kyr BP (2.3‰ and -1.1‰, respectively) and were significantly higher at ~4.4 cal kyr BP (8.8‰ and 29.2‰, respectively). Likewise, relatively higher values (8.2‰ and 29.8‰, respectively) were recorded at ~2.9 cal kyr BP. Thereafter, the isotopic ratios increased until the present (11.4‰ and 37.1‰, respectively), suggesting increasing aridity and/or hydrological closeness of the lake. A relative minimum in δ<sup>18</sup>O and δD occurred at ~2.3 cal kyr BP, during the wetter stage of the Iberian Roman Humid Period, while a relative maximum at ~1.1 cal kyr BP was recorded during the Medieval Warm Period.</p><p>We use a steady-state Isotope Mass Balance to investigate the paleo-hydrological conditions in the lake setting at different stages of the Holocene. Our results suggest that at ~11.2 cal kyr BP La Ballestera Playa-lake was a flow-through lake closely connected to the aquifer with and evaporation/outflow ratio <0.5. At 4.4 cal kyr BP and from ~2.9 cal kyr BP until the present, the system behaved as a terminal lake (evaporation/outflow ratio close to 1), with less connection to the aquifer and the main water output occurred via evaporation. The studied system turned into a playa lake because of a regional water table lowering. This most likely resulted from increasing aridity in southern Iberia during the late Holocene, which has previously been suggested by other lake sediment records in this region. </p><p> </p><p><strong>Acknowledgement</strong></p><p>This study was supported by the Junta del Andalucía PY18-871 to FG, the project<strong> </strong>CGL2017-85415-R of the Ministerio de Economía y Competitividad of Spain and Fondo Europeo de Desarrollo Regional FEDER, the project B-RNM-144-UGR18, Proyectos I+D+i del Programa Operativo FEDER 2018 and the research groups RNM-189 y RNM-190 (Junta de Andalucía). Dr. Antonio García-Alix acknowledges the Ramón y Cajal fellowship, RYC-2015-18966. Fernando Gázquez acknowledges the postdoctoral “HIPATIA” program of University of Almería.</p>

Investigation of dynamic lake changes in Zhuonai Lake–Salt Lake Basin, Hoh Xil, using remote sensing images in response to climate change (1989–2018)

The area covered by the four lakes in the Zhuonai Lake–Salt Lake Basin in Hoh Xil (Zhuonai Lake, Kusai Lake, Heidinor Lake, and Salt Lake) has changed significantly over the past 30 years. In this study, remote sensing image data gathered via the Landsat thematic mapper, enhanced thematic mapper plus, and operational land imager from 1989 to 2018 were used to extract the areal parameters of four lakes. The total area of the four lakes had increased by 18% in the past 30 years due to climate change. Interpolated results based on the meteorological data from 28 meteorological stations in the basin were used for trend analysis. A single-layer lake evaporation model was utilized to study the changes in the annual lake evaporation in the basin. The annual lake evaporation slightly increased from 1989 to 1995, followed by a sharp decrease from 1995 to 2018. From 1989 to 2018, the annual evaporation in the basin ranged between 615.37 and 921.66 mm, with a mean of 769.73 mm. A mass balance model was developed to estimate the changes in the lake volumes due to precipitation and evaporation. The increase in precipitation and the decrease in the annual lake evaporation promote the expansion of the four lakes. Lake evaporation is the main factor inducing changes in the lake areas.