Long-term Water Level Fluctuations Research Articles

Soil aggregate disintegration effects on soil erodibility in the water level fluctuation zone of the Three Gorges Reservoir, China

Spatial hydrological alterations can affect soil structural stability. Over time, forces induced by water weaken soil aggregates and this has a negative implication to soil health. The Three Gorges Reservoir (TGR) in particular, experienced a long-term hydrological condition and repetitive seasonal water level fluctuations that could affect soil health. The present study was conducted to investigate the effects of different water levels on soil aggregate disintegration rate over time and its relation to soil erosion susceptibility in water reservoirs. Samples from different elevations (155 m, 160 m, 163 m, 166 m, 172 m, and 180 m) in the water level fluctuation zone (WLFZ) were exposed to continuous wet-shaking for 3, 9, 27, 54, and 81 min resulted to different WLF intensity accordingly. The results showed a comparative difference between aggregates size before and after the experiment where micro-aggregates (<0.25 mm) increased with respect to elevations increase. The exponential prediction proved that aggregate stability decreased with the increase of WLF intensity, insisting the effects of continuous hydrological stress to aggregate break-down. A couple of factors definitely confirmed that soil erodibility (k) is primarily determined by disintegration of soil aggregates for the surface soil of the TGR. Despite the fact that Disintegration rate (Dr) and k showed a positive relationship, R2 = 0.73 (p < 0.05), the results showed that the soil properties decreasing Dr also decreases soil erodibility in the study area. Non-effective role of soil organic matter (SOM) for stabilizing soil aggregates was primarily related to water level fluctuations inhibiting decomposition. Relying on the present findings, environmental problems mostly soil erosion in the TGR could be therefore linked to excessive destabilization of soil aggregates. Therefore, the results of this study should play a major role in determining the factors primarily inducing soil erosion in river reservoirs.

Long-Term Water Level Fluctuations in Terminal Lakes of Central Asia

Long-Term Water Level Fluctuations in Terminal Lakes of Central Asia

Improving coastal resilience planning with respect to long-term water level fluctuations by examining decadal coastal profile behavior at sandy, harbor filet beaches along Lake Michigan in the Great Lakes of North America

Resilient planning for coastal hazards requires an understanding of both short-term and long-term coastal change dynamics. Numerous studies have been conducted throughout the Great Lakes of North America on processes and responses associated with short-term coastal changes, such as storms and seasonal fluctuations in lake level; however, few datasets exist that can capture long-term coastal morphodynamics in this region. Lack of data and knowledge creates a barrier for accurately modeling future coastal change, which underpins proactive coastal management. This is particularly problematic at sites adjacent to coastal infrastructure, such as those near harbors. To address this, we utilize a 32-year record of coastal profile change from several sites along the Lake Michigan shoreline of Michigan to examine profile evolution in response to changing lake levels and human disturbance. These data reveal that coastal sites without shoreline armoring can recover from erosive high lake level phases if lake level remains low for an extended period. However, if sites are armored, or if future climate conditions result in more frequent or more extreme lake level fluctuations, full recovery of the coastal profile is unlikely. Managers and decisionmakers can utilize this information to evaluate their site conditions and proactively plan for future coastal changes.

Structural damage to carbonate pillar hazardous rock masses subject to long-term water-level fluctuations in the Three Gorges reservoir area, China

Given the wide distribution of carbonate pillars in the Three Gorges reservoir area, there is a need to investigate the possible structural damage they experience from long-term water-level fluctuations. This study analysed the coupled effects of an improved time-dependent crack propagation pattern and failure modes of structural rock masses under stress-seepage using the Jianchuandong pillar hazardous rock mass (JCD) as a case study. A new crack simulation method based on FLAC 3D is proposed in which the interface element is immediately set on the surface of the yielding zone during the calculation step when a zone yields under tensile or shear stress. The two zones are directly separated during the tension or shearing of the bond at the contact surface. The JCD simulations illustrated that fractures and failure zones within the rock mass would propagate along the existing vertical cracks and extend to the base toe. The base rock mass would experience fracturing, finally leading to failure of the entire rock mass. The presented model provides sufficiently accurate predictions and is a suitable method for analysing time-dependent failure of pillar hazardous rock masses subject to water-level fluctuations. Thematic collection: This article is part of the Role of water in destabilizing slopes collection available at: https://www.lyellcollection.org/cc/Role-of-water-in-destabilizing-slopes

Effects of hydrological forcing on short- and long-term water level fluctuations in Lake Huron-Michigan: A continuous wavelet analysis

Understanding water level fluctuation patterns in the Great Lakes is one of the pillars for designing adaptive management practices that can mitigate the impacts of extreme water levels on shoreline infrastructure and associated economic activities. The present study uses continuous wavelet transformation to conduct a two-dimensional frequency-scale spectral analysis on monthly water levels in Lake Huron-Michigan. Consistent with past work, we detected 1-, 8-, 12-, and 36-year quasi-state periodicities in water level records during the 1860–2015 period. The wavelet analysis revealed diminishing, re-emergent, and/or intermodulation patterns in the long-term periodicities, but the 1-year cycle has persisted throughout the temporal domain studied. While the features of the dominant frequencies are consistent with previous findings, the consideration of wavelet ridges with the continuous wavelet transformation yielded a complete picture of evolution in time–frequency domain that is impossible to achieve with the same accuracy using conventional signal processing methods. Continuous wavelet transformation and analysis of wavelet coherence between hydrological and water level changes signified the role of runoff and evaporation as the primary drivers of water level fluctuations in Lake Huron-Michigan. Evaporation strongly influences the annual water level fluctuations, whereas runoff and precipitation covary with the water levels in both intraannual and interannual cycles. Specifically, analysis of phase differences indicated that runoff leads water level change by π/4 rad from 2-month up to 1.5-year cycles, then runoff starts to become nearly in-phase (with small intermittent lags) up to the 12-year cycle, two main recurring cycles of 0.5- and 1-year. Finally, we conducted a comprehensive assessment of 16,809 regression models, which highlighted the effects of runoff-minus-evaporation in modulating the extreme high or low water levels, which in turn could inundate the areas close to the shoreline or reduce the navigability in shallow parts of Lake Huron-Michigan.

Towards a Correlation between Long-Term Seawater Intrusion Response and Water Level Fluctuations

Laboratory and numerical experiments were conducted to provide a quantitative steady-state analysis of the effect of incremental variations of water level on saltwater intrusion. The purpose was to seek mathematical correlations relating both the wedge toe length and the height along the coastline to the boundary head difference. The laboratory experiments were completed in a 2D sand tank where both freshwater and seawater levels were varied. The experiments were conducted for two bead sizes having different hydraulic conductivities. The numerical model SEAWAT was used to validate the results and then to perform sensitivity analysis. The experimental results show that at steady-state conditions, the logarithmic toe length could be expressed as a linear function of the boundary head difference. The linear relationship was recorded in both advancing and receding wedge phases. The linearity of the correlation was also well demonstrated with analytical solutions. Similar relationships were also derived in the scenarios where the sea level fluctuated while the freshwater boundary head was constant. The height of the saltwater wedge along the coastline was also found to be a linear function of the boundary head difference. The sensitivity analysis shows that the regression coefficients were sensitive to the hydraulic conductivity, the dispersivity, and the saltwater density, while the porosity and the rate of boundary head change induced negligible effects. The existence of a linear relationship between the logarithmic toe length and the boundary head difference was also well evidenced in a field-scale aquifer model for all the different hydrogeological aquifer conditions tested. This study is the first attempt in identifying the underlying correlation between the boundary water level variations and the main seawater intrusion (SWI) external metrics under controlled laboratory conditions, which is of great relevance from a water resources management perspective.

Deformation mechanisms and evolution of a pile-reinforced landslide under long-term reservoir operation

Stabilizing piles are widely used for reinforcing landslides in the Three Gorges Reservoir area, China. Due to reservoir operations, long-term water-level fluctuations (WLFs) may cause instability or failure of the reservoir landslide and piles system (RLPS). This study experimentally investigated the deformation characteristics and mechanisms of the RLPS under long-term WLFs. The results showed that long-term WLFs led to loading and unloading cycles and consequently a weakening of the slope stability, where retrogressive failure and system instability were observed. Retrogressive failure at the slope toe was caused by topographical variation and physical and mechanical deterioration, which may be a result of the long-term WLFs. System instability was accompanied by a stress-release process above the new slip surface and was determined to be dependent on the geological structure of the RLPS. Based on this investigation, the evolution model of the pile-reinforced landslide under long-term WLFs was proposed. Even though the RLPS was adversely affected by the long-term WLFs, it maintained a relatively steady state due to the reinforcement of the piles. Effective pile installation changed the development of the reservoir landslides and prevented the entire slip surface from reaching a critical state. Thus, a catastrophic consequence was avoided, except for the local failure. Through physical modeling, this study experimentally provided a deeper understanding of the deformation mechanisms and evolution of the RLPS influenced by the long-term WLFs.

Impact of long-term water level fluctuation on the distribution, transport, and fate of phosphorus in reservoir sediment.

Water level fluctuation zone (WLFZ) with changeable environmental conditions would affect the transport and release of nutrients in the sediment. To investigate the influence of long-term water level fluctuations on sediment phosphorus (P), a reservoir sediment partitioning method based on historical water level was developed and applied in the Biliuhe Reservoir. The reservoir sediment was divided into frequent fluctuation zone (FFZ), fluctuation zone of continuous droughts (DFZ), and continuously submerged zone (CSZ). Sediment cores in different zones were collected and P was analyzed. TP content in the surface sediment progressively increased from FFZ, DFZ, to CSZ except the 0-10-cm samples of D1, and TP content of sediment cores increased gradually with decreasing depth except D1 core. Ferric iron-bound P (Fe-P) and organic P (OP) exhibited uniform spatial variation with TP, while no clear patterns were found with regard to the other forms. Fe-P composed most of TP (54.67 ± 10.15%) and had a significant positive correlation with stable OP (5.55 ± 2.07%). The contributions of Fe-P, detrital apatite P (Det-P), and OP are stable among the four cores, indicating that the relationship between the various P forms is relatively stable despite variations in environmental conditions of WLFZ. The alternation of deposition and erosion under long-term water level fluctuation can promote P transport down-flow, which can be prevented by the continuous growth of plants in WLFZ. Thus, the reasonable use of the plant growth in WLFZ can control the P load of the reservoir.

Impacts of water level fluctuations on the physicochemical properties of black carbon and its phenanthrene adsorption-desorption behaviors

The stability of black carbon (BC) as a slow cycling pool in the global C cycle is an important property and is likely governed by environmental conditions. Although the importance of role of the water regime in BC degradation was confirmed, direct impacts of water level fluctuations (WLF) on BC degradation were absent. This study investigated the changes in the physicochemical properties of BC and the behaviors of adsorption-desorption due to long-term WLF. The results showed that BC in the zone of WLF in soil contained higher amounts of carbon and lower amounts of oxygen, leading to contain few carboxylic functional groups and indicating that the WLF imposed on the reservoirs have altered BC decomposition, causing a decrease in mineralization. Furthermore, BC exhibited higher adsorption capacities and an apparent sorption–desorption hysteresis. Our results suggested that WLF has an advantageous role in preventing BC decomposition. Such protection has significance for the stability of BC in soils as well as for its effects on global C cycling and HOCs sorption. Understanding the decomposition mechanisms, dynamics and environmental influences should provide new insights into BC degradation and cycling.

Use of the Effective Monthly Recharge model to assess long-term water-level fluctuations in and around groundwater-dominated wetlands

Effective Monthly Recharge (Wem) calculations use historical weather data to estimate monthly-scale water level changes in precipitation-and-groundwater-driven wetlands. This time-weighted water-budget procedure relates first-of-the-month hydraulic heads measured in a monitoring well or small pond with precipitation and evapotranspiration data for preceding months and generates a regression equation used to estimate historic water levels. This study developed an enhanced procedure more robust than used with previous Wem studies. Two data sets of water-table fluctuations in humid-temperate southeastern Virginia (U.S.A.) allowed verification of the model procedure—a 30-year record from a shallow well maintained by the U.S.G.S., and a 6.5-year record from a mitigation wetland measured before and after construction. Analyses of Predicted Heads and Observed Heads at both sites indicate that the Wem model can replicate reasonably the seasonal patterns of water-table fluctuations and the range of values of hydraulic heads at a monthly scale. Within the limitations set by the assumptions of the procedure and the range of water fluctuations during the calibration period, Wem calculations may be used to generate synthetic hydrographs for periods with appropriate weather data. Analyses of two sites in Missouri and Nebraska (U.S.A.) suggest that the Wem procedure may prove useful also in climatic regions with relatively strong seasonal forcing, but additional testing is needed to verify the range of model applicability. These reconstructions could support long-term decisions in the management of wildlife habitats or design of mitigation wetlands.

Linking the distribution of microbial deposits from the Great Salt Lake (Utah, USA) to tectonic and climatic processes

Abstract. The Great Salt Lake is a modern hypersaline lake, in which an extended modern and ancient microbial sedimentary system has developed. Detailed mapping based on aerial images and field observations can be used to identify non-random distribution patterns of microbial deposits, such as paleoshorelines associated with extensive polygons or fault-parallel alignments. Although it has been inferred that climatic changes controlling the lake level fluctuations explain the distribution of paleoshorelines and polygons, straight microbial deposit alignments may underline a normal fault system parallel to the Wasatch Front. This study is based on observations over a decimetre to kilometre spatial range, resulting in an integrated conceptual model for the controls on the distribution of the microbial deposits. The morphology, size and distribution of these deposits result mainly from environmental changes (i.e. seasonal to long-term water level fluctuations, particular geomorphological heritage, fault-induced processes, groundwater seepage) and have the potential to bring further insights into the reconstruction of paleoenvironments and paleoclimatic changes through time. New radiocarbon ages obtained on each microbial macrofabric described in this study improve the chronological framework and question the lake level variations that are commonly assumed.

The response of south taiga forest ecosystems of European Russia to climatic changes in the Holocene

This study combines different methods, including grain size, macrofossil, and pollen analyses, to reconstruct paleogeographical and paleoclimatological conditions for periods before, during, and after the isolation of a small lake (Lake Kachishayoot) in northern Québec. After the retreat of the Laurentide Ice Sheet around 8000 14C yr B.P., the area was submerged by the Tyrrell Sea. The transition from marine to lacustrine environment occurred about 5400 yr B.P. Two major periods of water-level fluctuations were inferred from organic and mineral sediments: a high water level that occurred after 3200 yr B.P. and a low water level that started before 2200 yr B.P. Our chronological data for the first period are consistent with those from nearby Lac des Pluviers and from other lakes in east central Canada and in the northeastern United States. During the low-water-level period, however, there is no evidence for minor fluctuations, whereas other lakes in northern Québec and east-central Canada underwent several brief lowerings. Long-term changes in atmospheric circulation caused by changing global boundary conditions likely explained long-term water-level fluctuations of Lake Kachishayoot.

Identification of Pumping Influences in Long-Term Water Level Fluctuations

Identification of the pumping influences at monitoring wells caused by spatially and temporally variable water supply pumping can be a challenging, yet an important hydrogeological task. The information that can be obtained can be critical for conceptualization of the hydrogeological conditions and indications of the zone of influence of the individual pumping wells. However, the pumping influences are often intermittent and small in magnitude with variable production rates from multiple pumping wells. While these difficulties may support an inclination to abandon the existing dataset and conduct a dedicated cross-hole pumping test, that option can be challenging and expensive to coordinate and execute. This paper presents a method that utilizes a simple analytical modeling approach for analysis of a long-term water level record utilizing an inverse modeling approach. The methodology allows the identification of pumping wells influencing the water level fluctuations. Thus, the analysis provides an efficient and cost-effective alternative to designed and coordinated cross-hole pumping tests. We apply this method on a dataset from the Los Alamos National Laboratory site. Our analysis also provides (1) an evaluation of the information content of the transient water level data; (2) indications of potential structures of the aquifer heterogeneity inhibiting or promoting pressure propagation; and (3) guidance for the development of more complicated models requiring detailed specification of the aquifer heterogeneity.

The Importance of Water Level Changes and Shoreline Development in the Eutrophication of a Shallow, Seepage Lake

Water level fluctuations, whether climatically induced or the result of artificial regulation, can have a profound effect upon lake processes, especially in shallow lakes. Confounding the impact of changing water levels is nutrient input resulting from anthropogenic changes in land use. Paleolimnological techniques were used in a shallow seepage lake to infer the importance of water level changes and shoreland development as a source of nutrients to the lake. A long-term record of lake level in a Wisconsin lake was obtained from the measurements obtained by residents, who measured the width of the beach in front of their property over 73 years. These measurements were converted to vertical elevation through a detailed survey in 2008. Additional lake elevations were inferred from a 110-year precipitation record. While the mean depth of the lake was 2.1 m, lake elevation fluctuated up to 2.4 m. Cottage development began in the 1920s, increased in the late 1930s and further increased in recent decades. The bulk sedimentation accumulation rate initially increased with early cottage development, but the rate tripled with intensified development in the latter part of the twentieth century. The increase in the sedimentation resulted from increased soil erosion. Even though erosional rates have declined in the last 2 decades, use of soil amendments, hydrated lime and synthetic fertilizers have resulted in additional nutrient input to the lake. Multivariate statistical techniques performed on the diatom community revealed the greater importance of phosphorus concentrations than changing lake elevation in structuring the diatom responses. This analysis suggested that shoreline development history was more important than changes in lake elevation as a source of nutrients to the lake. This shallow, seepage lake was much more responsive to landuse changes than to long-term water level fluctuations.

Temporal scales of water-level fluctuations in lakes and their ecological implications

Water-level fluctuations (WLF) of lakes have temporal scales ranging from seconds to hundreds of years. Fluctuations in the lake level generated by an unbalanced water budget resulting from meteorological and hydrological processes, such as precipitation, evaporation and inflow and outflow conditions usually have long temporal scales (days to years) and are here classified as long-term WLF. In contrast, WLF generated by hydrodynamic processes, e.g. basin-scale oscillations and travelling surface waves, have periods in the order of seconds to hours and are classified as short-term WLF. The impact of WLF on abiotic and biotic conditions depends on the temporal scale under consideration and is exemplified using data from Lake Issyk-Kul, the Caspian Sea and Lake Constance. Long-term WLF induce a slow shore line displacement of metres to kilometres, but immediate physical stress due to currents associated with long-term WLF is negligible. Large-scale shore line displacements change the habitat availability for organisms adapted to terrestrial and aquatic conditions over long time scales. Short-term WLF, in contrast, do not significantly displace the boundary between the aquatic and the terrestrial habitat, but impose short-term physical stress on organisms living in the littoral zone and on organic and inorganic particles deposited in the top sediment layers. The interaction of WLF acting on different time scales amplifies their overall impact on the ecosystem, because long-term WLF change the habitat exposed to the physical stress resulting from short-term WLF. Specifically, shore morphology and sediment grain size distribution are the result of a continuous interplay between short- and long-term WLF, the former providing the energy for erosion the latter determining the section of the shore exposed to the erosive power.

Long-term and seasonal water level fluctuations of the Rybinsk Reservoir and their role in the functioning of its ecosystem

Seasonal and long-term variability of the Rybinsk Reservoir level regime over the period of its operation was analyzed. Changes in the level regime at different phases of water content were shown together with the data on mean monthly and extreme level values and the rates of the reservoir filling and drawdown. The level regime impact on the functioning of individual components of the reservoir ecosystem was discussed. Due consideration was given to the assessment of changes in the reservoir environmental situation under the condition of the normal impounded water level drop by 1 m.

Untangling the confounding effects of urbanization and high water level on the cover of emergent vegetation in Cootes Paradise Marsh, a degraded coastal wetland of Lake Ontario

An approach based on a digital elevation model (DEM) was used to untangle the confounding effects of long-term water-level fluctuations and increasing human population on the cover of emergent vegetation in Cootes Paradise Marsh, a degraded coastal wetland in Lake Ontario, Canada. Data for 20 observations between 1934 and 1993 were used in the analysis. First, we calculated the inundated area based on the DEM, a derived measurement that reflected the bathymetry of the marsh and the mean water level for a particular year. Then Mantel correlations and regression analyses were used to analyze the relationships between emergent cover and corresponding water level, inundated area, and human population, respectively. Results of the simple and partial correlations indicated that areal change of emergent plants was significantly correlated with inundated area after controlling for the effect of water level fluctuation; however, there was no significant correlation between emergent cover and water level after controlling for inundated area. This is an important consideration when multiple sites from the same Great Lake are compared since the same water level may correspond to vastly different inundated areas for different marshes. Changes in emergent cover were also significantly correlated with human population after controlling for water level effects. Altogether, inundated area explained 83.1% of the variation, human population explained 4.2%, and the interaction between population and inundated area explained an additional 4.3% of the remaining variation in areal emergent cover. This indicates that the synergistic effect of high water level (expressed as inundated area) and increased human population induced greater detrimental impact on the emergent plants than did either stressor alone.

Isolation and water-level fluctuations of Lake Kachishayoot, Northern Québec, Canada

This study combines different methods, including grain size, macrofossil, and pollen analyses, to reconstruct paleogeographical and paleoclimatological conditions for periods before, during, and after the isolation of a small lake (Lake Kachishayoot) in northern Québec. After the retreat of the Laurentide Ice Sheet around 8000 14C yr B.P., the area was submerged by the Tyrrell Sea. The transition from marine to lacustrine environment occurred about 5400 yr B.P. Two major periods of water-level fluctuations were inferred from organic and mineral sediments: a high water level that occurred after 3200 yr B.P. and a low water level that started before 2200 yr B.P. Our chronological data for the first period are consistent with those from nearby Lac des Pluviers and from other lakes in east central Canada and in the northeastern United States. During the low-water-level period, however, there is no evidence for minor fluctuations, whereas other lakes in northern Québec and east-central Canada underwent several brief lowerings. Long-term changes in atmospheric circulation caused by changing global boundary conditions likely explained long-term water-level fluctuations of Lake Kachishayoot.

Historical aerial photographs and a geographic information system (GIS) to determine effects of long-term water level fluctuations on wetlands along the St. Marys River, Michigan, USA

The water levels of the Great Lakes fluctuate as much as ± 1 m from their respective long-range mean elevations in response to changes in climatic conditions. Coastal wetland areas on each Great Lake expand or contract in response to the long-term water level fluctuations. The water level of the St. Marys River, a connecting channel between Lakes Superior and Huron, is largely controlled by the level of Lake Huron. The St. Marys River wetlands expand and contract in a fashion similar to wetlands on the lakes. Data on St. Marys River wetland areas were derived from historical aerial photographs and placed in a Geographic Information System (GIS) to analyze the effects of water level fluctuations. The GIS was used to measure wetland area changes between the years for which photographic data were available. Use of GIS allowed quantification of wetland area changes, estimation of response rates and description of inter-class transfer dynamics, for five coastal wetland classes influenced by long-term water level fluctuations.

The Physical Effects of the Great Lakes on Tributaries and Wetlands

Wetlands and tributary confluences are susceptible to physical influences imposed by the Great Lakes, particularly through the effects of short and long-term water level fluctuations and accompanying transport disruptions including flow and transport reversals. With there being few, if any, direct field observations of these disruptions based upon velocity measurements, the objective of this paper is to review the possible physical effects on these regions by first, reviewing the relevant contributing physics known about the Great Lakes; second, contrasting possible marine estuary transport mechanisms with what little is published about the Great Lakes circumstances; and third, summarizing modeled results exemplifying these behaviors from a study ofSandusky Bay, Lake Erie. Because it exhibits the strongest response to storms and the clearest measureable signals resulting from them, attention is centered on Lake Erie. In contrast to a typical research paper, the objective herein is to provide a summary of what is known and commonly accepted about these physics which can serve as a backdrop for the other papers in this special issue.