Low Reservoir Levels Research Articles

It's not all about drought: What “drought impacts” monitoring can reveal

Drought impacts monitoring has been called the missing piece in drought assessment. The potential to improve drought management is high but uncertain due to rare analyses of impacts datasets, predominantly because there are few impacts monitoring programmes to generate the datasets. Drought impacts monitoring is conducted on the ground in much of Brazil by local observers at monthly and municipality scale to support the Brazilian Drought Monitor. In Ceará state, within drought-prone semiarid northeast Brazil, over 3600 drought impacts reports were completed by agricultural extension officers from 2019 to 2022. We investigated, through manual coding and observer interviews, the reported drought impacts and impact drivers. Analysis provided a catalogue of the experienced impacts and showed that impacts still occur, and are often normalised, during non-drought periods, sometimes as lingering effects of previous droughts. The impact drivers were predominantly non-extreme hydrometeorological conditions or a result of socio-technical vulnerabilities such as insufficient water infrastructure. The normalisation of “impacts” included, in particular: a generally accepted high level of crop losses and consistently low reservoir levels around which the agricultural and domestic systems are adapted. Conventional drought indices often did not align with experienced impact severity, highlighting the limitations of relying solely on these indices for emergency response. Continual impacts monitoring could be extremely valuable anywhere in the world for identifying vulnerabilities and informing proactive measures to reduce drought and other hazard risk, in addition to guiding targeted mitigation efforts.

Напряженно-деформированное состояние плотины Юмагузинского гидроузла

Introduction. The stone-and-earth dam of the Yumaguzinskiy hydroelectric complex on the Belaya river is constructed in complicated geological conditions on heterogeneous foundation. The results of computational research of stress-strain state (SSS) of the dam, carried out for the variant of an earth dam with the central core are presented. When calculating the deflected mode of dams, the real structure of ground characterized by its relation of elastic and plastic bonds should be taken into account. The change of this structure takes place along with the change in stresses and is reflected in the values of coefficient of relative strength and coefficients of reliability. The values of the safety coefficients can be used to judge the strength state of the dam. Materials and methods. The stress-strain state of the dam was determined on the basis of the energy model of the developed by L.N. Rasskazov. The area of the selected fragment of the dam has been divided into single-type elements; a triangular grid of the finite element method has been adopted, by means of which the structure of the soil dam and the foundation have been described. Results. Numerical calculations have shown that when water level in the reservoir rises to the level of the forced retaining level the character of stress distribution σxx changes. At the base of uppermost buttress prism at the boundary with the core there appears an area with small positive values, the largest of which is obtained in the transition zone. The entire hydrostatic load is transferred to the pressure face of the core and, consequently, the entire work of external forces is transferred to the internal deformation energy of this element, causing a stress concentration in it. The transition zone material is forced to follow the deformations of the core, resulting in the development of tensile stresses in the core. Therefore, increasing the stiffness of the core results in less deformation of the core and correspondingly less tensile stress in the transition zone. The nature of stress distribution σyy is symmetrical. Conclusions. Increasing the rigidity of the core entails elimination of the arch effect, which is particularly noticeable at lower reservoir levels. For this reason the use of skeleton material in the core of the dam is desirable.

Featured Collection Introduction: Severe Sustained Drought Revisited: Managing the Colorado River System in Times of Water Shortage 25 Years Later — Part I

Featured Collection Introduction: Severe Sustained Drought Revisited: Managing the Colorado River System in Times of Water Shortage 25 Years Later — Part I

Water Storage Decisions and Consumptive Use May Constrain Ecosystem Management under Severe Sustained Drought

AbstractDrought has impacted the Colorado River basin for the past 20 years and is predicted to continue. In response, decisions about how much water should be stored in large reservoirs and how much water can be consumptively used will be necessary. These decisions have the potential to limit riverine ecosystem management options through the effect water‐supply decisions have on reservoir elevations. We used projected hydrology and river temperatures to compare the outcome of combinations of water storage scenarios and consumptive use limits on metrics associated with ecosystem management of the Colorado River in Grand Canyon. Ecosystem management metrics included the ability to implement designer flows, temperature suitability for fishes, and fragmentation. We compared current water management operations to prioritizing storage in either Lake Mead or Lake Powell combined with three levels of consumptive use. Projected reservoir levels limited environmental flow delivery and increased fragmentation regardless of where water was stored if consumptive use was not limited. Warmer river temperatures associated with low reservoir levels are likely, creating suitable conditions for non‐native species of concern, such as smallmouth bass. Water storage decisions provided variability and management flexibility, but water storage was less important when less water was available, highlighting the importance of keeping water in the system to provide flexibility for achieving ecosystem goals.

Virtual water flow and water footprint as optimizer of water resource management in the state of Ceará, Brazil

The water exported indirectly by sending products to other countries, or vice versa, is called a virtual water flow and this can be measured through water footprint (WF) calculations, which represent the embedded water needed to manufacture a product. This present study aims to analyze the virtual water flow and the WF of the main products exported by municipalities in the state of Ceará in the year 2019, in order to enhance the management of the state’s water resources. Analytical hierarchy process (AHP), the most commonly used multicriteria decision-making method in the world, was used to determine which product is more sustainably produced by the municipalities of Ceará, with the criteria: WF, price, and volume exported. The alternatives are at least two of the seven categories of products exported by the state where the “fruit or vegetable juices” class was preferred as the most sustainable. It was found that most cities in the state that export agricultural products use only one basin, which can lead to very low reservoir levels, while the other hydrographic basins in the state are underused. It is worth noting that the Metropolitan Basin concentrates on 11 out of 32 municipalities that export abroad and that it is responsible for supplying more than 4,074,730 inhabitants, according to Brazilian Institute of Geography and Statistics (IBGE, 2019).

Susceptibility of reservoir-induced landslides and strategies for increasing the slope stability in the Three Gorges Reservoir Area: Zigui Basin as an example

The construction of the huge Three Gorges reservoir affected a large region, and the resultant geological and environmental impacts have caused global concern. The remarkable, 30-m annual fluctuation in the reservoir water level poses a significant threat to slope stability in this area. Four hundred sixty-two landslides were identified in the Zigui basin using historical records, satellite images, field investigations and unmanned aerial vehicle (UAV) observations, enabling the construction of a complete landslide database and distribution map. Three failure modes of landslides in the Zigui basin are used to illustrate the major factors that govern reservoir-induced landslides. The results show that (1) > 99% of identified landslides occur on slopes angle <47°, while >80% occur at elevations below 600 m; (2) Jurassic Niejiashan Formation is highly prone to landslides; (3) Low reservoir levels of 145 m to 155 m greatly reduce slope stability. Based on the information entropy method that use the conditional probability of different influencing factors and principal component analysis as inputs, the relative contributions of various influencing factors are quantified and a landslide susceptibility map was drawn. This susceptibility map helps define the countermeasures that will best reduce fatalities and property losses for areas having different landslide conditions and susceptibilities.

Beyond ‘Day Zero’: insights and lessons from Cape Town (South Africa)

Acute water security vulnerability at regional to local scales is becoming increasingly apparent. In 2017, officials in Cape Town, South Africa, designated the term “Day Zero” to demark an exact time when the city’s taps would be switched off due to critically low reservoir levels. Beyond Day Zero, residents would need to converge at communal water collection points to access a 25-L daily ration of water. The particulars of the crisis and stakeholder responses prove informative to other cities.

Qualitative and quantitative HIV antibodies and viral reservoir size characterization in vertically infected children with virological suppression.

Absence of detectable viraemia after treatment cessation in some vertically HIV-infected (VHIV) children suggests that early initiation of HAART could lead to functional cure. We described the factors associated with HIV antibody levels and the viral reservoir size in HAART-treated VHIV children. Study included 97 VHIV children with virological suppression, in Bamako, Mali. The anti-gp41 antibody activities and HIV serostatus were assessed. The viral reservoir size was measured by quantifying total cell-associated HIV DNA. Among the children studied, the median total HIV DNA level was 445 copies/10 6 cells (IQR = 187-914) and the median anti-gp41 antibody activity was 0.29 OD (IQR = 0.18-0.75). Low activity of anti-gp41 antibodies was associated with a younger age of HAART initiation ( P = 0.01). Overall, eight HIV-1 seroreversions were identified. Study identified potential candidates with low viral reservoir and low antibody levels or activities for future trials aiming to reduce HIV-1 reservoir to limit HAART duration.

Management Options During the 2011-2012 Drought on the Apalachicola River: A Systems Dynamic Model Evaluation.

The Apalachicola-Chattahoochee-Flint River basin (ACF) is a large watershed in the southeastern United States. In 2012, the basin experienced the second year of a severe drought and the third multi-year drought in the last 15years. During severe droughts, low reservoir and river levels can cause economic and ecological impacts to the reservoir, river, and estuarine ecosystems. During drought, augmenting Apalachicola River discharge through upstream reservoir releases and demand management are intuitive and often-suggested solutions to minimizing downstream effects. We assessed whether the existing reservoir system could be operated to minimize drought impacts on downstream water users and ecosystems through flow augmentation. Our analysis finds that in extreme drought such as observed during 2012, increases in water releases from reservoir storage are insufficient to even increase Apalachicola River discharge to levels observed in the 2007 drought. This suggests that there is simply not enough water available in managed storage to offset extreme drought events. Because drought frequency and intensity is predicted to increase under a variety of climate forecasts, our results demonstrate the need for a critical assessment of how water managers will meet increasing water demands in the ACF. Key uncertainties that should be addressed include (1) identifying the factors that led to extremely low Flint River discharge in 2012, and (2) determining how water "saved" via demand management is allocated to storage or passed to downstream ecosystem needs as part of the ongoing revisions to the ACF Water Control Manual by the US Army Corps of Engineers.

Combined ART started during acute HIV infection protects central memory CD4+ T cells and can induce remission.

Therapeutic control of HIV replication reduces the size of the viral reservoir, particularly among central memory CD4+ T cells, and this effect might be accentuated by early treatment. We examined the effect of ART initiated at the time of the primary HIV infection (early ART), lasting 2 and 6 years in 11 and 10 patients, respectively, on the HIV reservoir in peripheral resting CD4+ T cells, sorted into naive (TN), central memory (TCM), transitional memory (TTM) and effector memory (TEM) cells, by comparison with 11 post-treatment controllers (PTCs). Between baseline and 2 years, CD4+ T cell subset numbers increased markedly (P < 0.004) and HIV DNA levels decreased in all subsets (P < 0.009). TTM cells represented the majority of reservoir cells at both timepoints, T cell activation status normalized and viral diversity remained stable over time. The HIV reservoir was smaller after 6 years of early ART than after 2 years (P < 0.019), and did not differ between PTCs and patients treated for 6 years. One patient, who had low reservoir levels in all T cell subsets after 2 years of treatment similar to the levels in PTCs, spontaneously controlled viral replication during 18 months off treatment. Early prolonged ART thus limits the size of the HIV reservoir, protects long-lived cells from persistent infection and may enhance post-treatment control.

The Stabilizing Effect of Hydro Reservoir Levels on Intraday Power Prices Under Wind Forecast Errors

The power system has to deal with three main sources of uncertainty: demand uncertainty and load prediction errors, failure of power plants and uncertainty of wind. The growing share of wind and other intermittent generation sources in the European supply increases the uncertainty about power production in day-ahead and longer-term predictions. As EU member states increase the deployment of wind power and other intermittent renewable energy sources, the intraday and balancing market will gain more interest, as additional demand for reserve and response operations is needed. Hence, it becomes relevant to analyse the effect of wind power forecasting errors on intraday power prices. A higher forecast error will increase the need of intraday markets to balance out the oversupply or deficit of wind power on an hourly basis. This oversupply or deficit can be corrected though flexible hydropower plants; however the power price is highly influenced by the fluctuations in the reservoir level (Huisman et. al [2013]). In this paper, we question to what extent hydropower a stabilizing effect has on the impact of wind forecast errors on NordPool intraday prices. To do so, we examine the peak and off peak imbalance power prices for the Scandinavian market (ELBAS) from 2011 until 2013 with a Markov regime-switching model in periods with low and high hydro reservoir levels. Results indicate that under wind forecast error, the use of hydropower capacity in intraday markets is proven to be an effective volatility control mechanism. However, the price stabilizing effect of hydropower capacity does not take place at all times.

Blimp-1 overexpression is associated with low HIV-1 reservoir and transcription levels in central memory CD4+ T cells from elite controllers.

The aim of the study was to determine the molecular mechanisms underlying the quasi-equilibrium between HIV and its host in the model of functional cure represented by elite controllers who spontaneously maintain exceptionally low levels of HIV reservoirs. Whole-genome transcriptional study and quantification of the cell-associated HIV DNA and HIV RNA levels of the four major resting CD4 T-cell subsets in HIV-1-infected elite controllers, viremic long-term nonprogressors (vir-LTNPs), and uninfected individuals. We compared the whole-genome transcriptional profiles (ArrayExpress accession number E-MTAB-1480) of the four major resting CD4 T-cell subsets [naive (TN), central-memory (TCM), transitional-memory (TTM), and effector-memory (TEM)] from 14 HIV-1-infected individuals including seven elite controllers (E-LTNPs) and seven vir-LTNPs, and from seven uninfected individuals. The HIV-1 cellular DNA and mRNA levels were quantified in parallel in each sorted subset. Host gene transcriptomes followed subset differentiation and viremia except in E-LTNPs wherein TCM, the main CD4 cell compartment, showed the highest activity with three specific signatures involving overexpression of T-cell receptor and costimulation signaling pathways, overexpression of the PRDM-1/Blimp-1 transcriptional repressor, and downmodulation of type-I IFN-related genes. Among subsets, the PRDM1/Blimp-1 upregulation was associated with lower levels of both cellular HIV-DNA and HIV mRNA levels. This unique Blimp-1 transcriptional repressor signature and the contrast between host and virus transcriptional activities in TCM from elite controllers suggest Blimp-1 might be involved in controlling the HIV reservoirs in the key TCM subset.

Water security through scarcity pricing and reverse osmosis: a system dynamics approach

Water supply and demand planning is often conducted independently of social and economic strategies. There are presently no comprehensive life-cycle approaches to modelling urban water balances that incorporate economic feedbacks, such as tariff adjustment, which can in turn create a financing capacity for investment responses to low reservoir levels. This paper addresses this gap, and presents a system dynamics model that augments the usual water utility representation of the physical linkages of water grids, by adding inter-connected feedback loops in tariff structures, demand levels and financing capacity. The model, applied in the south-east Queensland region in Australia, enables simulation of alternatives and analysis of stocks and flows around a grid or portfolio of bulk supplies including an increasing proportion of rain-independent desalination plants. Such rain-independent water production plants complement the rain-dependent sources in the region and can potentially offer indefinite water security at a price. The study also shows how an alternative temporary drought pricing regime not only defers costly bulk supply infrastructure but actually generates greater price stability than traditional pricing approaches. The model has implications for water supply planners seeking to pro-actively plan, justify and finance portfolios of rain-dependent and rain-independent bulk water supply infrastructure. Interestingly, the modelling showed that a temporary drought pricing regime not only lowers the frequency and severity of water insecurity events but also reduces the long-run marginal cost of water supply for the region when compared to traditional reactive planning approaches that focus on restrictions to affect demand in scarcity periods.

The Stabilizing Effect of Hydro Reservoir Levels on Intraday Power Prices Under Wind Forecast Errors

The power system has to deal with three main sources of uncertainty: demand uncertainty and load prediction errors, failure of power plants and uncertainty of wind. The growing share of wind and other intermittent generation sources in the European supply increases the uncertainty about power production in day-ahead and longer-term predictions. As EU member states increase the deployment of wind power and other intermittent renewable energy sources, the intraday and balancing market will gain more interest, as additional demand for reserve and response operations is needed. Hence, it becomes relevant to analyse the effect of wind power forecasting errors on intraday prices. A higher forecast error will increase the need of the use of intraday markets to balance out the oversupply or deficit of wind on hourly basis. This oversupply or deficit can be corrected though flexible hydropower plants; however the power price is highly influenced by the fluctuations in the reservoir level (Huisman et. al [2013]). In this paper, we question to what extent hydropower has a stabilizing effect on the impact of wind forecasting errors on NordPool intraday prices. To do so, we examine the hourly imbalance power prices for the Scandinavian market (ELBAS) from 2011 until 2013 with two Markov regime-switching models for periods with low and high hydro reservoir levels during base, peak and off peak hours. Results indicate that under wind forecast error, the use of hydropower capacity in intraday markets is proven to be an effective volatility control mechanism. However, the price stabilizing effect of hydro reservoir levels do not take place in all possible times. Therefore, additional flexible generation capacity is needed to act in times where, from the water management nature, hydropower it is not providing stability.

Drought and the water–energy nexus in Texas

Texas experienced the most extreme drought on record in 2011 with up to 100 days of triple digit temperatures resulting in record electricity demand and historically low reservoir levels. We quantified water and electricity demand and supply for each power plant during the drought relative to 2010 (baseline). Drought raised electricity demands/generation by 6%, increasing water demands/consumption for electricity by 9%. Reductions in monitored reservoir storage <50% of capacity in 2011 would suggest drought vulnerability, but data show that the power plants were flexible enough at the plant level to adapt by switching to less water-intensive technologies. Natural gas, now ∼50% of power generation in Texas, enhances drought resilience by increasing the flexibility of power plant generators, including gas combustion turbines to complement increasing wind generation and combined cycle generators with ∼30% of cooling water requirements of traditional steam turbine plants. These reductions in water use are projected to continue to 2030 with increased use of natural gas and renewables. Although water use for gas production is controversial, these data show that water saved by using natural gas combined cycle plants relative to coal steam turbine plants is 25–50 times greater than the amount of water used in hydraulic fracturing to extract the gas.

On the risk premium in Nordic electricity futures prices

This paper examines empirically the relationship between electricity spot and futures prices, by analysing a decade of data for a set of short term-to-maturity futures contracts traded in the Nordic Power Exchange. It is found that, on average, there are significant positive risk premiums in short-term electricity futures prices. The significance and size of the premiums, however, varies seasonally over the year; whereas it is greatest during winter, it is zero in summer. It is also found that time-varying risk premiums are significantly related to unexpectedly low reservoir levels. Furthermore, before the unprecedented supply-shock that hit the market around the end of year 2002, the risk premiums were related to the variance and the skewness of future spot prices.

Riverine and Reservoir Influences on Year Class Strength and Growth of Upper Great Plains Paddlefish

A long-term investigation (1991–2006) was conducted on the relation between Yellowstone and Missouri River discharges, water level (elevation) changes of Lake Sakakawea, a Missouri River mainstem reservoir in western North Dakota, and the ecology of the Yellowstone-Sakakawea stock of paddlefish Polyodon spathula, a zooplanktivorous Acipenseriform fish. After impoundment in December 1953, Lake Sakakawea filled gradually over a 13-year period (1953–1966). Water levels were lowered sharply and briefly in 1977 and 1981 and for much more prolonged periods of 1988–1993 and 2000–2006 associated with drought conditions in the central United States and water management decisions by the U.S. Army Corps of Engineers. The 1995 year class of paddlefish, by far the strongest in the 16-year study period, was associated with the sharp rise in water level from August 1993 through 1995, the longest continuous rise since the initial filling and the only period since initial filling when reservoir levels rose substantially in three consecutive years. High reservoir levels were associated with higher densities of zooplankton (all taxa combined and Leptodora kindtii, the primary food of age 0 paddlefish), stronger year classes (based on counts of age 0 fish along standard transects), greater mean weight and condition of age 0 fish in August, greater mean weights of recruits, higher growth rate of adult fish, and greater weight of gonadal fat bodies (GFBs), an indicator of energy storage, in absolute weight, as a percentage of gonad weight, and as a percentage of fish weight. Sixty-three percent of the variation in the ratio of GFB weight/gonad weight was explained by reservoir level. Fish tagged as adult migrants and recaptured in succeeding years after rearing in rising and high reservoir conditions gained an average of 0.04 kg/yr, whereas fish rearing in falling- and low-reservoir conditions lost an average of 0.19 kg/yr. Missouri River discharge during spring was significantly correlated with estimated age 0 year class strength, but a similar relationship did not hold for the Yellowstone River, which is the river used by most spawning paddlefish. Results of this study are consistent with studies from Lake Sakakawea and other reservoirs indicating that trophic upsurge in recently filled (and refilled) reservoirs favors the development of stronger year classes, faster growth, better condition, and larger size at maturity of fishes. Higher riverine discharges, thought to favor paddlefish reproductive success, were also typically associated with a rising or high reservoir. In contrast, low-reservoir levels over the period 2000–2006 have negatively affected paddlefish year class strength, growth, and energy storage. If, in succeeding years, Lake Sakakawea once again is allowed to rise to full pool as it did over the period 1993–1995, inundation of the shorelines and the vegetation can be expected to result in another upsurge period and a resulting benefit to paddlefish. Effective management of water levels in Lake Sakakawea for the benefit of paddlefish and other fishes will require a more balanced approach between upper basin and lower basin Missouri River interests.

Short-Term Electricity Futures Prices: Evidence on the Time-Varying Risk Premium

This paper examines empirically the relationship between electricity spot and futures prices, by analysing a decade of data for a set of short term-to-maturity futures contracts traded in the Nordic Power Exchange, Nord Pool. It is found that, on average, there are significant positive risk premiums in short-term electricity futures prices. The significance and size of the premiums, however, varies seasonally over the year; whereas it is greatest during winter, it is zero in summer. It is also found that time-varying risk premiums are significantly related to unexpectedly low reservoir levels. Furthermore, before the unprecedented supply-shock that hit the Nord Pool market around the end of year 2002, the variation of the risk premiums was related to the variance and the skewness of future spot prices. This result is consistent with the view that risk considerations played a role in the determination of futures prices. Finally, additional evidence provided throughout the paper supports the view that circumstances changed in the Nord Pool market after the shock period.

Hydraulic characteristics of partial opening of the working gate for a discharge tunnel

The partial opening of the working gate for a discharge tunnel is used more and more widely in the various conditions, such as releasing discharge to meet the needs of the various stages under construction, or of the operations at low reservoir levels. In this article the hydraulic characteristics were investigated of the partial opening of the working gate based on the physical model experiments of the discharge tunnel for the Longtan Hydropower Project, including the discharge coefficient, the surface profile of the free flow section, the bottom pressure distribution of the tunnel with an aerator, the cavity length just from the ramp, and the wall pressure of the curve section of the outlet. Some new issues were discussed and the properties were presented of the partial opening of the gate.

Use of a Low-Prime Circuit for Bloodless Heart Transplantation in Xenotransplant of 5—7 Kilogram Primates

There is a great effort to decrease blood product use during open-heart surgery in pediatrics. We were presented with a research challenge to accomplish heart xenotransplantation from donor cynomologous monkey (Macaca fascicularis) to recipient olive baboon (Papio anubis) of 5–7 kilograms without benefit of donor or banked blood products. The purpose of this study was to design and implement a practical, low-volume circuit to minimize hemodilution and avoid the use of blood products. A simple circuit was assembled using a low-volume oxygenator with hardshell venous reservoir, an 1/8-inch arterial line, an 1/4-inch venous line, and gravity drainage. Three xenotransplants were performed and evaluated. The mean recipient weights were 6.3 ± 0.7 kg. Circuit prime volume was 228 ± 5.8 mL, and bypass time was 85 ± 6.7 min. Blood flow rates were 585 ± 113 mL/min with postmembrane arterial line pressures of 344 ± 81 mmHg, and patient mean arterial pressures (MAP) of 51.4 ± 16.7 mmHg. Venous saturations were 63.7 ± 8.0%. The hematocrit prebypass was 37.4 ± 3.2, bypass 20.7 ± 0.9, post-MUF 27.8 ± 3.3, and 7 days postoperative 24.5 ± 7.5%. Platelet count was 289 ± 1.1 K/µL, 147 ± 37.1 K/µL, and 322 ± 292.7 K/µL prebypass, postbypass, and 7 days postoperative, respectively. Plasma-free hemoglobin prebypass was 7.5 ± 4.4 mg/dL and postbypass 22.2 ± 16.5 mg/dL with no noted hematuria during and after the procedure. All patients survived and were successfully weaned from cardiopulmonary bypass (CPB) with same day extubation. A low-prime circuit for bloodless heart surgery is possible. To achieve low reservoir levels, especially without the use of an arterial line filter (ALF), it is necessary to have a full armament of monitoring and alarm devices.