Gorges Reservoir In China Research Articles

Effects of Water Temperature on Chlorophyll-a Concentration Stratification in the Tributary Bay of Three Gorges Reservoir

AbstractThis study aims to quantitatively investigate the formation mechanism of concentration stratification for chlorophyll-a in thermal-stratified water bodies. A well-validated, three-dimensional hydrodynamic-water temperature model was established and applied to simulate the water temperature distribution in Xiangxi Bay (XXB), a representative tributary bay of the Three Gorges Reservoir in China. The numerical results show that temperature stratification with stable vertical temperature profiles seasonally occurred in XXB. Based on these findings, the effect of water temperature stratification on the vertical transport of suspended solids was discussed. Using theoretical derivation and analysis of the relationship between water temperature and the settling velocity of a single spherical solid particle, the settling velocity of suspended solids was significantly affected by temperature under weak turbulence. Therefore, the suspended solids tended to accumulate in the epilimnion or thermocline regions,...

Study on Duration for Perilous Rock to Form

As one geological disaster in the area of the Three Gorges Reservoir of China, perilous rocks dominate stability of slopes in the area. Most cliffs or steep slopes are alternately composed of inflexible rock such as sandstone and soft rock such as mudstone in the area, and due to different weathering velocities rock cells in soft rock below inflexible rock are usually developed. Any perilous rock belongs to a part of inflexible rock. To appraise the safety of perilous rock, it is essential to approach duration for perilous to form is of interest. In the present paper, authors analyze weathering velocity of rock cell and establish method to calculate length of critical rock cell. Duration for perilous rock to form can be divided into three parts, (1) duration to form critical rock cell, (2) damage duration of control fissure, and (3) fracture duration of control fissure. Further, methods to calculate these durations are established in details based on damage mechanics and fracture mechanics.

Dynamic risk assessment of oil spill scenario for Three Gorges Reservoir in China based on numerical simulation

A novel method for dynamic risk assessment of oil spill accidents based on numerical simulation was presented in this paper. The dynamic risk assessment model was developed consisting of a comprehensive list of caused consequences like environmental damage, asset loss, health impact and social effect as well as emergency actions preventing these losses. Contributing events in the Mater Logic Diagram (MLD) of the dynamic risk assessment model were valued based on the simulated evolvement of oil contaminants under spill scenario on quasi-static fluid, which was obtained by coupling an oil spill model with hydrodynamic module in Jialing river of Three Gorges Reservoir in China after the impoundment of the reservoir to 175m water level in 2010. Calculated result of dynamic risk as grade IV indicated that the assessed oil spill was not as catastrophic as we thought because of the slow transport of oil fractions on water surface and absence of dispersed oil in water body due to the quasi-static fluid, very gentle wind and effective emergency actions, as well as by the reason that rare agriculture or industrial crops exist in spill adjacent area.

Gravity Recovery and Climate Experiment (GRACE) detection of water storage changes in the Three Gorges Reservoir of China and comparison with in situ measurements

Water impoundment in the Three Gorges Reservoir (TGR) of China caused a large mass redistribution from the oceans to a concentrated land area in a short time period. We show that this mass shift is captured by the Gravity Recovery and Climate Experiment (GRACE) unconstrained global solutions at a 400 km spatial resolution after removing correlated errors. The WaterGAP Global Hydrology Model (WGHM) is selected to isolate the TGR contribution from regional water storage changes. For the first time, this study compares the GRACE (minus WGHM) estimated TGR volume changes with in situ measurements from April 2002 to May 2010 at a monthly time scale. During the 8 year study period, GRACE‐WGHM estimated TGR volume changes show an increasing trend consistent with the TGR in situ measurements and lead to similar estimates of impounded water volume. GRACE‐WGHM estimated total volume increase agrees to within 14% (3.2 km3) of the in situ measurements. This indicates that GRACE can retrieve the true amplitudes of large surface water storage changes in a concentrated area that is much smaller than the spatial resolution of its global harmonic solutions. The GRACE‐WGHM estimated TGR monthly volume changes explain 76% (r2 = 0.76) of in situ measurement monthly variability and have an uncertainty of 4.62 km3. Our results also indicate reservoir leakage and groundwater recharge due to TGR filling and contamination from neighboring lakes are nonnegligible in the GRACE total water storage changes. Moreover, GRACE observations could provide a relatively accurate estimate of global water volume withheld by newly constructed large reservoirs and their impacts on global sea level rise since 2002.

Seed submergence tolerance of four annual species growing in the water-level-fluctuation zone of Three Gorges Reservoir, China, and effects of long-term submergence on their seed germination

Aims Our objective was to examine seeds of Echinochloa crusgalli, Xanthium sibiricum, Aeschynomene indica and Polygonum hydropiper, four common annual species growing in the water-level-fluctuation zone of Three Gorges Reservoir in China, in regard to tolerance of submergence and germination in the changing environment of the zone. Methods We divided the water-level-fluctuation zone into nine elevational zones according to the Wusong Elevation criterion. We then observed seed submergence tolerance and the effects of submergence on seed germination in a "water impoundment-water recession" cycle after seeds of the four species were sown in the nine elevational zones. Seed germination was divided into seeds with and without sand sediment on surface. Important findings Ripe seeds (or fruits) of the four species kept their vitality after submergence. The starting time for seed germination after the end of submergence and seed germination duration both gradually decreased with decreasing elevation (p 0.01), and the starting time for seed germination was significantly reduced below 169 m (p 0.01). Overall, within the same elevational zone, the starting time for seed germination after the end of submergence was longest for A. indica, followed by X. sibiricum, and shortest for P. hydropiper. For E. crusgalli, X. sibiricum and P. hydropiper, seed germination percentage first increased and then decreased with decreasing elevation, while it decreased for A. indica. Sand sedimentation had little effect on seed germination; the effect waspositive for X. sibiricum and negative for A. indica. We concluded that seeds (or fruits) of the four annuals can tolerate submergence and germinate successfully in the changing environment of water-level-fluctuation zone. Therefore, these species are useful in the revegetation and restoration of this zone of the Three Gorges Reservoir.

Deriving multiple near‐optimal solutions to deterministic reservoir operation problems

Even deterministic reservoir operation problems with a single objective function may have multiple near‐optimal solutions (MNOS) whose objective values are equal or sufficiently close to the optimum. MNOS is valuable for practical reservoir operation decisions because having a set of alternatives from which to choose allows reservoir operators to explore multiple options whereas the traditional algorithm that produces a single optimum does not offer them this flexibility. This paper presents three methods: the near‐shortest paths (NSP) method, the genetic algorithm (GA) method, and the Markov chain Monte Carlo (MCMC) method, to explore the MNOS. These methods, all of which require a long computation time, find MNOS using different approaches. To reduce the computation time, a narrower subspace, namely a near‐optimal space (NOSP, described by the maximum and minimum bounds of MNOS) is derived. By confining the MNOS search within the NOSP, the computation time of the three methods is reduced. The proposed methods are validated with a test function before they are examined with case studies of both a single reservoir (the Three Gorges Reservoir in China) and a multireservoir system (the Qing River Cascade Reservoirs in China). It is found that MNOS exists for the deterministic reservoir operation problems. When comparing the three methods, the NSP method is unsuitable for large‐scale problems but provides a benchmark to which solutions of small‐ and medium‐scale problems can be compared. The GA method can produce some MNOS but is not very efficient in terms of the computation time. Finally, the MCMC method performs best in terms of goodness‐of‐fit to the benchmark and computation time, since it yields a wide variety of MNOS based on all retained intermediate results as potential MNOS. Two case studies demonstrate that the MNOS identified in this study are useful for real‐world reservoir operation, such as the identification of important operation time periods and tradeoffs among objectives in multipurpose reservoirs.

Development of optical criteria to discriminate various types of highly turbid lake waters

Our aim was to refine the optical classification of turbid waters in order to improve the performance of water color algorithms. Bio-optical measurements and sampling of optically active substances were performed in highly turbid lakes Taihu, Chaohu, and Dianchi, and in Three Gorges reservoir in China. Based on strong correlations between trough depths of remote sensing reflectance (R rs(λ)) near 680 nm (denoted as TD680) and the ratios of inorganic suspended matter (ISM) to total suspended matter (TSM) concentrations, an empirical model was developed for water classification. In the 400–900 nm spectral range, different correlations between R rs(λ), TSM and chlorophyll a (Chla) concentrations indicate discrepancies among the following ISM/TSM ranges: ISM/TSM ≤ 0.5, 0.5 < ISM/TSM < 0.8, and ISM/TSM ≥ 0.8. Corresponding findings support an important conclusion that only high ISM/TSM ratios, usually above 0.5, and using the more sensitive and stable near infrared spectral range (730–820 nm), can assure good performances of the TSM remote sensing algorithms. Meanwhile, the particulate absorption a p(λ) and scattering b p(λ) were strongly influenced by different ranges of ISM/TSM ratios. Typically the a p(675) peaks became more and more vague as ISM/TSM increased, and the b p(λ) values first decreased and then increased with a marked inflexion at ISM/TSM ≈ 0.5. The TD680 threshold values were derived to discriminate three types of turbid waters, i.e., Type 1 (TD680 ≥ 0.0082 sr−1), Type 2 (0.0082 sr−1 > TD680 > 0 sr−1), and Type 3 (TD680 ≤ 0 sr−1). This study provides a promising tool for identifying various types of highly turbid waters, and is significant for the development of class-based algorithms of water color remote sensing.

Method to calculate fatigue fracture life of control fissure in perilous rock

Rupture and safety of perilous rock are dominated by control fissure behind perilous rock block. Based on model-I and model-II stress strength factors of control fissure under acting of weight of perilous rock, water pressure in control fissure and earthquake forces, method to calculate critical linking length of control fissure is established. Take water pressure in control fissure as a variable periodic load, and abide by P-M criterion, when control fissure is filled with water, establish the method to calculate fatigue fracture life of control fissure in critical status by contributing value of stress strength factor stemming from water pressure of control fissure in Paris’s fatigue equation. Further, parameters (C and m) of sandstone with quartz and feldspar in the area of the Three Gorges Reservoir of China are obtained by fatigue fracture testing.

Triaxial-Compression Testing Method Developed for Small Rock Specimens

Estimation of physical properties of rock is essential to design rock structures and to evaluate the stability of rock slopes. It is well known that rock properties often vary from site to site, and even from specimen to specimen. So, in many cases, it requires many rock samples, much effort and cost to obtain the reliable data. In this study, an efficient testing method with small rock specimens was proposed and examined. At first, the preparation process for a cylindrical specimen, 10mm in diameter and 20mm in length, was developed. In the experimental work, the transparent triaxial vessel, developed by Okubo et al., was modified and used for the small specimen. Triaxial compression tests with constant loading rate were conducted with small specimens of Tage tuff, and it was found that cohesion, C, and angle of internal friction, φ, can be precisely obtained. By this test, the loading rate dependency of a stress-strain curve can be also obtained by just one small specimen with the loading rate alternately switching during a test. Small specimens are easy to carry and it is effective especially for geophysical researches in foreign countries. So, in this study, triaxial compression tests, noted above, were also conducted with rocks obtained around the Three Gorges Reservoir in China.

Landslides along the bank of the Yangtze Gorges Reservoir in China : Wang, G X Proc 5th International Symposium on Landslides, Lausanne, 10–15 July 1988V2, P1259–1261. Publ Rotterdam: A A Balkema, 1988

Landslides along the bank of the Yangtze Gorges Reservoir in China : Wang, G X Proc 5th International Symposium on Landslides, Lausanne, 10–15 July 1988V2, P1259–1261. Publ Rotterdam: A A Balkema, 1988