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.

Dynamically Driven Inflow onto the Galactic Center and its Effect upon Molecular Clouds

The Galactic bar plays a critical role in the evolution of the Milky Way’s Central Molecular Zone (CMZ), driving gas toward the Galactic Center via gas flows known as dust lanes. To explore the interaction between the CMZ and the dust lanes, we run hydrodynamic simulations in arepo, modeling the potential of the Milky Way’s bar in the absence of gas self-gravity and star formation physics, and we study the flows of mass using Monte Carlo tracer particles. We estimate the efficiency of the inflow via the dust lanes, finding that only about a third (30% ± 12%) of the dust lanes’ mass initially accretes onto the CMZ, while the rest overshoots and accretes later. Given observational estimates of the amount of gas within the Milky Way’s dust lanes, this suggests that the true total inflow rate onto the CMZ is 0.8 ± 0.6 M ⊙ yr−1. Clouds in this simulated CMZ have sudden peaks in their average density near the apocenter, where they undergo violent collisions with inflowing material. While these clouds tend to counter-rotate due to shear, co-rotating clouds occasionally occur due to the injection of momentum from collisions with inflowing material (∼52% are strongly counter-rotating, and ∼7% are strongly co-rotating of the 44 cloud sample). We investigate the formation and evolution of these clouds, finding that they are fed by many discrete inflow events, providing a consistent source of gas to CMZ clouds even as they collapse and form stars.

Hydrodynamic model of the formation of horizontal drainage runoff on drainless and slightly drained irrigated lands in the dry steppe zone of Ukraine

The article presents the results of the research, which are the basis of making a hydrodynamic model of the formation of drainage runoff of closed horizontal drainage on drainless and slightly drained irrigated lands in the dry steppe zone of Ukraine. The relevance of the research is in their need when designing the systems of horizontal drainage, determining drain spacing, modes of operation and the evaluation of drainage efficiency during its operation when irrigating with the use of modern sprinklers from a closed farm network. The objective of the research is to develop a generalized hydrodynamic model of formation of closed horizontal drainage runoff when irrigating from a closed farm network on drainless and slightly drained lands, which are typical for the watershed plains and coastal lowlands of the dry steppe zone of Ukraine. The task of the research to determine the basic conditions and factors of formation of horizontal drainage runoff, to specify the structure of groundwater inflow to the drains when having optimal drain spacing in the closed farm network and to define the prospects and areas of further research. Research methods and techniques: long-term (1975-2020) field experiments on drained areas with different drain spacing in typical hydrogeological conditions for watersheds and coastal lowlands; water balance studies; theoretical research methods (analysis and synthesis, comparison, generalization, zoning); to determine the structure of groundwater inflow to the drains, the method of electrohydrodynamic analogies when using the laboratory integrator EGDA 9/60 was applied. As a result of the research it was determined that in the conditions of a closed water farm network it is possible to increase drain spacing from 120-220 m to 240-400 m. When studying all the conditions of drainless and slightly drained watershed plains and coastal lowlands, the main sources forming the regime of groundwater and drainage runoff are the precipitation of 420 mm or 55.0% of water input, irrigation water - 340 mm or 45.0%, including 266 mm or 35,0% from irrigation and 75 mm or 10,0% from filtration from the canals. The analysis of the hydrodynamic model of drainage runoff formation shows that when having drain spacing as 240-400 m, the inflow from the zone located above the bottom of the drain is 2.6-4.8% of the total inflow to the drain. The ascending flow under the bottom of the drain enters it at an average angle of 600 and in all variants of drain spacing is 95.2-97.2% of the total inflow. When drain spacing increases from 240 to 300-400 m, the horizontal inflow from the area located below the bottom of the drain decreases with a corresponding increase in the ascending flow under the bottom of the drain. The average width of the ascending flow to the drain at the edge of the active zone of groundwater (9.0-10.0 m below the drain) is 13.0-20.0 m. The resulting model complements the existing theoretical and methodological knowledge base for designing horizontal drainage and is necessary in perspective researches on the formation of expert systems for optimization of the parameters and modes of irrigation and drainage functioning when applying modern broadcast sprinkler equipment irrigating from the closed farm network.

Using Stable Isotopes to Determine the Water Balance of Utah Lake (Utah, USA)

To investigate the hydrology of Utah Lake, we analyzed the hydrogen (δ2H) and oxygen (δ18O) stable isotope composition of water samples collected from the various components of its system. The average δ2H and δ18O values of the inlets are similar to the average values of groundwater, which in turn has a composition that is similar to winter precipitation. This suggests that snowmelt-fed groundwater is the main source of Utah Valley river waters. In addition, samples from the inlets plot close to the local meteoric water line, suggesting that no significant evaporation is occurring in these rivers. In contrast, the lake and its outlet have higher average δ-values than the inlets and plot along evaporation lines, suggesting the occurrence of significant evaporation. Isotope data also indicate that the lake is poorly mixed horizontally, but well mixed vertically. Calculations based on mass balance equations provide estimates for the percentage of input water lost by evaporation (~47%), for the residence time of water in the lake (~0.5 years), and for the volume of groundwater inflow (~700 million m3) during the period April to November. The short water residence time and the high percentage of total inflow coming from groundwater might suggest that the lake is more susceptible to groundwater pollution than to surface water pollution.

General Assessment of the Operational Utility of National Water Model Reservoir Inflows for the Bureau of Reclamation Facilities

This work investigates the utility of the National Oceanic and Atmospheric Administration’s National Water Model (NWM) for water management operations by assessing the total inflow into a select number of reservoirs across the Central and Western U.S. Total inflow is generally an unmeasured quantity, though critically important for anticipating both floods and shortages in supply over a short-term (hourly) to sub-seasonal (monthly) time horizon. The NWM offers such information at over 5000 reservoirs across the U.S., however, its skill at representing inflow processes is largely unknown. The goal of this work is to understand the drivers for both well performing and poor performing NWM inflows such that managers can get a sense of the capability of NWM to capture natural hydrologic processes and in some cases, the effects of upstream management. We analyzed the inflows for a subset of Bureau of Reclamation (BoR) reservoirs within the NWM over the long-term simulations (retrospectively, seven years) and for short, medium and long-range operational forecast cycles over a one-year period. We utilize ancillary reservoir characteristics (e.g., physical and operational) to explain variation in inflow performance across the selected reservoirs. In general, we find that NWM inflows in snow-driven basins outperform those in rain-driven, and that assimilated basin area, upstream management, and calibrated basin area all influence the NWM’s ability to reproduce daily reservoir inflows. The final outcome of this work proposes a framework for how the NWM reservoir inflows can be useful for reservoir management, linking reservoir purposes with the forecast cycles and retrospective simulations.

General Assessment of the Operational Utility of National Water Model Reservoir Inflows for Bureau of Reclamation Facilities

This work investigates the utility of the National Oceanic and Atmospheric Administration’s National Water Model (NWM) for water management operations by assessing the total inflow into a select number of reservoirs across the Central and Western U.S. Total inflow is generally an unmeasured quantity, though critically important for anticipating both floods and shortages in supply over a short-term (hourly) to sub-seasonal (monthly) time horizon. The NWM offers such information at over 5,000 reservoirs across the U.S., however, its skill at representing inflow processes is largely unknown. The goal of this work is to understand the drivers for both well performing and poor performing NWM inflows such that managers can get a sense of the capability of NWM to capture natural hydrologic processes and in some cases, the effects of upstream management. We analyzed the inflows for a subset of Bureau of Reclamation (BoR) reservoirs within the NWM over the long-term simulations (retrospectively, seven years) and for short, medium and long-range operational forecast cycles over a one-year period. We utilize ancillary reservoir characteristics (e.g. physical and operational) to explain variation in inflow performance across the selected reservoirs. In general, we find that NWM inflows in snow-driven basins outperform those in rain-driven, and that assimilated basin area, upstream management, and calibrated basin area all influence the NWM’s ability to reproduce daily reservoir inflows. The final outcome of this work proposes a framework for how the NWM reservoir inflows can be useful for reservoir management, linking reservoir purposes with the forecast cycles and retrospective simulations.

Simulating rainfall runoff and assessing low impact development (LID) facilities in sponge airport

The appearance of extreme weather causes frequent airport flooding, which has a serious impact on the normal operation of an airport. In this study, three simulation scenarios are set in order to study the effect of low impact development (LID) facilities (green roof and vegetative swale) on the water depth of overflow junctions and total inflow to the study area outlet in an airport at different rainfall return periods (2 a, 5 a, 20 a and 50 a). Vegetative swale has better reduction effect on water depth of overflow junctions than has green roof. The reduction rate of vegetative swale is about 25–52% at different rainfall return periods, but the effect of green roof is not obvious. For the double peak rainstorm, the reduction effect on the water depth of overflow junctions after setting vegetative swale for the first rain peak is better than that for the second rain peak. Under the condition of 2 a, 5 a, and 20 a, the total inflow reduction rates of study area outlet after applied green roof and vegetative swale are 16.85%, 20% and 22.17% respectively, and the effect is poor (only 2.26%) at low-frequency return period (50 a). This study can provide theoretical guidance for the design of LID facilities of a sponge airport.

Description of steady inflow of fluid to wells with different configurations and various partial drilling-in

There are many equations of steady inflow of fluid to the wells depending on the type of well, presence or absence of artificial or natural fractures passing through the well, different degrees of drilling-in of the wellbores. For some complex cases, analytical solutions describing the inflow of fluid to the well have not yet been obtained. An alternative to many equations is the use of numerical methods, but this approach has a significant disadvantage – a considerable counting time. In this regard, it is important to develop a more general analytical approach to describe different types of wells with different formation drilling-in and presence or absence of fractures. Creation of this method is possible during modeling of fractures by a set of nodes-vertical wells passing from a roof to floor, and modeling of a wellbore (wellbores, perforation) by a set of nodes – spheres close to each other. As a result, based on this approach, a calculation algorithm was developed and widely tested, in which total inflow to the well consists of the flow rate of each node taking into account the interference between the nodes and considering the impermeable roof and floor of the formation. Performed modeling confirmed a number of known patterns for horizontal wells, perforation, partial drilling-in of a formation, and also allowed solving a number of problems.

Application of A Tank Model to Assess the Performance of Rotiklot Reservoir Initial Filling

Rotiklot dam is located in Belu Regency that has the tropic climate, with very short wet season (4-5 months) and a very long dry season (7-8 months). The average monthly rainfall in December – April of approximately 300 – 500 mm/month, while in another month only ranges 30- 60 mm/month. During the rainy season, rainwater will overflow as surface water and collect in the river as a flood toward the sea. The construction of a dam is one alternative to overcome the water needs of the community during the dry season. The Rotiklot dam retains the flow of water in the Motamuru River and its reservoir can accommodate 2.9 million m3. Impounding is a process carried out once a dam has been constructed. It is a comprehensive process involving filling time and water inflow. The purpose of this study was to determine the first filling time and the inflow volume in Rotiklot Reservoir in the years of dry, low, normal and sufficient water using the Tank method. It aimed to simulate the initial filling of the reservoir. Also, the study is expected to evaluate the most suitable Tank model, with parameters calibrated using the Genetic Algorithm optimization approach. The determination coefficient using a four series tank is 0.531 greater than the coefficient obtained from 3 series tank simulation, which was 0.506. The total inflow volume in Rotiklot Reservoir for dry, low, normal and sufficient were 1.946, 7.289, 9.699, 13.822 million m3 respectively. Based on the calculation result of the inflow volume of the year of the low water, the filling time is around three months, starting from mid-December to mid-March.

Bottlenecks, Shockwave, and Off-Ramp Blockage on Freeways

Freeway congestion may spill back for several kilometers, blocking a number of on/off-ramps upstream. As a consequence, flows at the off-ramps may be substantially reduced, and vehicles bound for the off-ramps are trapped in the mainstream congestion, causing intensified spillback of congestion that blocks even more off-ramps further upstream. Such off-ramp blockage is readily understood and its impact is empirically recognized, but there is a lack of analysis to provide more insights. In this paper, some flow conditions for the activation of bottlenecks and congestion propagation are first established, and the mechanism of the off-ramp blockage is theoretically explored. Macroscopic and microscopic simulations are conducted to demonstrate the analytical results, and some general relations between the total demand, total inflow, total off-ramp outflow, and the number of vehicles within a freeway system are examined.