Long-term Water Level Changes Research Articles

Wave Climate Associated With Changing Water Level and Ice Cover in Lake Michigan

Detailed knowledge of wave climate change is essential for understanding coastal geomorphological processes, ecosystem resilience, the design of offshore and coastal engineering structures and aquaculture systems. In Lake Michigan, the in-situ wave observations suitable for long-term analysis are limited to two offshore MetOcean buoys. Since this distribution is inadequate to fully represent spatial patterns of wave climate across the lake, a series of high-resolution SWAN model simulations were performed for the analysis of long-term wave climate change for the entirety of Lake Michigan from 1979 to 2020. Model results were validated against observations from two offshore buoys and 16 coastal buoys. Linear regression analysis of significant wave height (Hs) (mean, 90th percentile, and 99th percentile) across the entire lake using this 42-year simulation suggests that there is no simple linear trend of long-term changes of Hs for the majority (>90%) of the lake. To address the inadequacy of linear trend analysis used in previous studies, a 10-year trailing moving mean was applied to the Hs statistics to remove seasonal and annual variability, focusing on identifying long-term wave climate change. Model results reveal the regime shifts of Hs that correspond to long-term lake water level changes. Specifically, downward trends of Hs were found in the decade of 1990–2000; low Hs during 2000–2010 coincident with low lake levels; and upward trends of Hs were found during 2010–2020 along with rising water levels. The coherent pattern between the wave climate and the water level was hypothesized to result from changing storm frequency and intensity crossing the lake basin, which influences both waves (instantly through increased wind stress on the surface) and water levels (following, with a lag through precipitation and runoff). Hence, recent water level increases and wave growth were likely associated with increased storminess observed in the Great Lakes. With regional warming, the decrease in ice cover in Lake Michigan (particularly in the northernmost region of the lake) favored the wave growth in the winter due to increased surface wind stress, wind fetch, and wave transmission. Model simulations suggest that the basin-wide Hs can increase significantly during the winter season with projected regional warming and associated decreases in winter ice cover. The recent increases in wave height and water level, along with warming climate and ice reduction, may yield increasing coastal damages such as accelerating coastal erosion.

Effects of Long-Term Nitrogen Fertilization and Ground Water Level Changes on Soil CO2 Fluxes from Oil Palm Plantation on Tropical Peatland

A long-term study on the effect of nitrogen (N) fertilization on soil carbon dioxide (CO2) fluxes in tropical peatland was conducted to (1) quantify the annual CO2 emissions from an oil palm plantation under different N application rates and (2) evaluate the temporal effects of groundwater level (GWL) and water-filled pore space (WFPS) on soil organic carbon (SOC) and CO2 fluxes. Monthly measurement of soil CO2 fluxes using a closed chamber method was carried out from January 2010 until December 2013 and from January 2016 to December 2017 in an oil palm plantation on tropical peat in Sarawak, Malaysia. Besides the control (T1, without N fertilization), there were three N treatments: low N (T2, 31.1 kg N ha−1 year−1), moderate N (T3, 62.2 kg N ha−1 year−1), and high N (T4, 124.3 kg N ha−1 year−1). The annual CO2 emissions ranged from 7.7 ± 1.2 (mean ± SE) to 16.6 ± 1.0 t C ha−1 year−1, 9.8 ± 0.5 to 14.8 ± 1.4 t C ha−1 year−1, 10.5 ± 1.8 to 16.8 ± 0.6 t C ha−1 year−1, and 10.4 ± 1.8 to 17.1 ± 3.9 t C ha−1 year−1 for T1, T2, T3, and T4, respectively. Application of N fertilizer had no significant effect on annual cumulative CO2 emissions in each year (p = 0.448), which was probably due to the formation of large quantities of inorganic N when GWL was temporarily lowered from January 2010 to June 2010 (−80.9 to −103.4 cm below the peat surface), and partly due to low soil organic matter (SOM) quality. A negative relationship between GWL and CO2 fluxes (p < 0.05) and a positive relationship between GWL and WFPS (p < 0.001) were found only when the oil palm was young (2010 and 2011) (p < 0.05), indicating that lowering of GWL increased CO2 fluxes and decreased WFPS when the oil palm was young. This was possibly due to the fact that parameters such as root activity might be more predominant than GWL in governing soil respiration in older oil palm plantations when GWL was maintained near or within the rooting zone (0–50 cm). This study highlights the importance of roots and WFPS over GWL in governing soil respiration in older oil palm plantations. A proper understanding of the interaction between the direct or indirect effect of root activity on CO2 fluxes and balancing its roles in nutrient and water management strategies is critical for sustainable use of tropical peatland.

Source of Oxygen Fed to Adventitious Roots of Syzygium kunstleri (King) Bahadur and R.C. Gaur Grown in Hypoxic Conditions.

Syzygium kunstleri, a woody plant species, adapts to hypoxic conditions by developing new adventitious roots. Here, we investigate its morphological adaptation to long-term water level changes and the sources and pathways of O2 supplied to its adventitious roots. Cuttings were cultivated in hydroponic and agar media, and then, the water level was increased by 6 cm following adventitious root emergence; afterward, O2 partial pressure changes were measured using a Clark-type O2 microelectrode. O2 concentrations in the adventitious roots decreased when N2 was injected, regardless of the presence of light, indicating that the O2 source was not photosynthetic when bark was removed. New adventitious roots developed near the surface when the water level increased, and O2 conditions above the raised water level influenced O2 concentrations in adventitious roots. O2 concentrations in adventitious roots that developed before the water level increased were lower than in the newly developed adventitious roots but increased when the O2 concentrations above the original water level increased. Our study highlights morphological changes, such as the development of adventitious roots, as environmental adaptation mechanisms. By revealing O2 sources in S. kunstleri under hypoxic environments, we offer insights into the challenges of long-term adaptation to changing environments in woody plants.

Do changes in water depth and water level influence the diatom diversity of Yunlong Lake, in Yunnan Province, Southwest China?

Exploring whether diatom diversity in a lake sediment core is representative of that of the entire lake is important for determining the response of lake diatom diversity to global climatic warming. In this study, Yunlong Lake, an alpine lake located in Yunnan Province, Southwest China, was investigated to explore this question over both space and time. Spatially, we investigated diatom diversity patterns in 62 surface sediment samples from different locations and depth zones of Yunlong lake and found essentially constant diatom diversity across the entire lake basin. Temporally, we studied a well-dated sediment core from the lake center to explore whether long-term water-level changes influenced diatom diversity over the last ~ 100 years. Changes in the annual average sediment accumulation rates indicate that the water level of Yunlong Lake increased substantially after the construction of a dam. However, there is no obvious relationship between diatom diversity and water-level changes, which suggests at this site long-term water-level changes did not influence diatom diversity. Comparative analysis of the results for Yunlong Lake with those for other lakes indicates that for relatively strongly mixed lakes with a simple morphology and uniform shoreline microhabitat, such as Yunlong Lake, differences in water depth and changes in water level may not influence diatom diversity. In such cases, the diatom diversity from a sediment core is likely to be representative of that of the entire lake during specific time intervals. Therefore, such lakes may be optimal for studies of changes in past diatom diversity using sediment cores.

How long-term water level changes influence the spatial distribution of fish and other functional groups in a large shallow lake

We numerically explored the effects of long-term water level changes on biotic biomass and spatial distribution of fish in a large shallow lake. We calibrated Ecospace model (Ecopath with Ecosim modelling suite) with data from various functional groups (ranging from phytoplankton to piscivorous fish), and considered 14 different habitats. Two scenarios representing, respectively, a long-term water-level increase and decrease by 1 m were constructed and run for a period of thirty eight years (1979–2016). The results showed a very uneven spatial distribution of fish biomass in the lake, with the highest concentration in the southern basin. The 1 m decrease scenario caused a diminution in the biomass of all groups but piscivorous fish. The 1 m increase scenario saw a weak decrease in most species biomass. Consequently, in both scenarios, long-term water level changes would be generally detrimental to the lake biota. In the context of more frequent climate-induced hydrological fluctuations, we encourage the use of these simulations as effective tools for future prediction and assessment of ecosystem-based fisheries management and ecological status maintenance of shallow lakes.

Unraveling the Role of Human Activities and Climate Variability in Water Level Changes in the Taihu Plain Using Artificial Neural Network

Water level, as a key indicator for the floodplain area, has been largely affected by the interplay of climate variability and human activities during the past few decades. Due to a nonlinear dependence of water level changes on these factors, a nonlinear model is needed to more realistically estimate their relative contribution. In this study, the attribution analysis of long-term water level changes was performed by incorporating multilayer perceptron (MLP) artificial neural network. We took the Taihu Plain in China as a case study where water level series (1954–2014) were divided into baseline (1954–1987) and evaluation (1988–2014) periods based on abrupt change detection. The results indicate that climate variables are the dominant driver for annual and seasonal water level changes during the evaluation period, with the best performance of the MLP model having precipitation, evaporation, and tide level as inputs. In the evaluation period, the contribution of human activities to water level changes in the 2000s is higher than that in the 1990s, which indicates that human activities, including the rapid urbanization, are playing an important role in recent years. The influence of human activities, especially engineering operations, on water level changes in the 2000s is more evident during the dry season (March-April-May (MAM) and December-January-February (DJF)).

Water level fluctuation in karst aquifers in the Transdanubian range (Hungary)

Monitoring of the karst aquifers of Transdanubian Range gives an opportunity to analyze not only the long-term water level and spring discharge changes, but also the short-term fluctuations. In thi...

MALAYSIAN SEA WATER LEVEL PATTERN DERIVED FROM 19 YEARS TIDAL DATA

Long-term water level changes have generally been estimated using tidal data. Tide gauges are common tools used to determine the continuous time series of relative water level. This paper presents an effort to interpret the water level from tidal data over Malaysian seas. There are 21 tide gauge stations involved and taken from Permanent Service for Mean Sea Level (PSMSL) with monthly averaged data from 1993 to 2011. The monthly tidal data is then converted to tidal sea level anomaly. For sea level trend analysis, robust fit regression is employed. Next, the sea levels were analysed based on the pattern of seasonal variation and extreme meteorological effects such as El-Nino and La-Nina. In summary, the relative sea level trend in Malaysian seas is rising and varying from 2 to 6.5 mm/yr. This study offers valuable sea level information to be applied in wide range of climatology, related environmental issue such as flood and global warming in Malaysia.

Effects of macrophyte development on the oxygen metabolism of an urban river rehabilitation structure

To compensate for fairway enlargements and the hydraulic impacts of navigation activity, an artificial rehabilitation structure was constructed in the urban, navigable River Spree in 2004. This wave-protected, shallow littoral zone proved to be highly effective in reducing vessel-induced waves and provided suitable conditions for the development of aquatic plants. However, in time it became less suitable for other aquatic organisms due to hypoxic conditions in late summer. This study aimed to comparatively calculate and analyze the oxygen balance of the rehabilitation structure and the main channel five years after the construction in 2009.In the rehabilitation structure, the production to respiration ratio ranged between 0.10 and 0.34 at the peak of vegetation density, while in the main channel in front of the rehabilitation structure it ranged between 0.67 and 0.86. Dense vegetation limited the water exchange and caused oxygen depletion. Thus, atmospheric oxygen input through the water surface and due to long-term water level changes became the most important supply processes for oxygen in the rehabilitation structure.Enhancing the oxygen supply to improve the suitability of the rehabilitation structure for other aquatic taxa requires an increase in water exchange with the main channel, e.g. by adaptively increasing the lateral connectivity.

14th-16th-Century Danube Floods and Long-Term Water-Level Changes in Archaeological and Sedimentary Evidence in The Western and Central Carpathian Basin: an Overview with Documentary Comparison

Abstract In the present paper an overview of published and unpublished results of archaeological and sedimentary investigations, predominantly reflect on 14th-16th-century changes, are provided and evidence compared to documentary information on flood events and long-term changes. Long-term changes in flood behaviour (e.g. frequency, intensity, seasonality) and average water-level conditions had long-term detectable impacts on sedimentation and fluvio-morphological processes. Moreover, the available archaeological evidence might also provide information on the reaction of the society, in the form of changes in settlement organisation, building structures and processes. At present, information is mainly available concerning the 16th, and partly to the 14th-15th centuries. These results were compared to the available documentary evidence on 14th-16th century Danube floods occurred in the Carpathian Basin.

Long-term and intraannual changes in run-off and water levels in the Volga River delta

Data of the State Observation Network on the water run-off for the whole observation period and on water levels in the delta of the Volga River for the period of regulated run-off regime (1961–2006) are analyzed. Periods of various water content are revealed and the current tendency of long-term run-off changes is established with the help of difference-integral curve of recovered natural annual run-off. Periods of various degree of man’s impact on the run-off, entering the delta of the Volga River, are marked out. The role of irretrievable anthropogenic loss and the influence of run-off regulation on its intraannual distribution are assessed. Regularities of seasonal and long-term water level changes in the delta of the Volga River are revealed. The run-off regulation effect on the intraannual distribution of water levels is assessed. The influence of the water divider on the redistribution of the run-off and water levels in the delta is shown. The effect of the current increase in the Caspian Sea level on the penetration of the backwater into the delta of the Volga River is revealed.

Long-Term Water Level Changes in Closed-Basin Lakes of the Canadian Prairies

The semi-arid prairie region of Canada has many closed-basin lakes that are sensitive to climatic variability and change. Long-term water level changes in these lakes provide a measure of the dynamic balance between runoff and precipitation supplying water to the lakes and water loss from the lakes by evaporation. Historic lake water level data can help to improve understanding and prediction of the hydrologic effects of climate change and land-use changes. Water level data for sixteen closed-basin lakes in the Canadian prairies were compiled from a variety of sources and additional measurements were made at some locations. In the Canadian prairie region there is an overall pattern throughout most of the twentieth century of declining lake levels, although with notable exceptions. Possible causes of lake level changes are assessed briefly, but the main objective is to present a regional and long-term perspective on lake level records.

Dynamic hydrologic model of the Örtülüakar Marsh in Turkey

A dynamic hydrologic model was developed for the Ortuluakar Marsh in Turkey to investigate the causes of water-level decreases observed since the 1990s and to explore potential remediation and sustainability options. Ortuluakar Marsh is a sub-system of the Sultan Marshes ecosystem, a large wetland complex consisting of freshwater marshes and salt-water lakes in the Develi Basin of south-central Turkey. The wetland has experienced significant seasonal and long-term waterlevel changes after the construction of an irrigation project in the catchment. The model uses a monthly time scale and solves the unsteady water-balance equation. Inputs from precipitation, overland flow, springs and ground water, and outputs due to evapotranspiration and surface flow are represented in the model. The model was calibrated to fit monthly water-level measurements from 1997 to 2003. Sensitivity analyses showed that the model is highly sensitive to evapotranspiration and ground-water inflow. Simulations of several water allocation options suggest that ground-water use should be reduced in the Develi Basin to halt the decline in water level in the Ortuluakar Marsh.

A Long-Lasting Relaxation of Seismicity at Aswan Reservoir, Egypt, 1982-2001

The Aswan reservoir seismicity is accepted as an example of reservoir- induced seismicity with the M 5.4 event of 1981, which occurred 15 years after the reservoir impoundment started. During the 1982-2001 period, the Aswan seismicity separates into shallow and deep seismic zones, between 0 and 15 and 15 and 30 km, respectively. These two seismic zones behave differently over time, as indicated by the seismicity rate, depth migration, b-value, and spatial clustering. For the deep events, the rate decreases with time, the depth remains at a constant or increasing depth, and the b-value is lower than for the shallow events, which migrate toward the surface with a close to constant seismicity rate. Of all the previous parameters, only the seismicity rate correlates with seasonal variations of the lake level. This is positive evidence for the Aswan reservoir seismicity to be reservoir triggered in the 1982-2001 period. Clustering over time and space expresses that numerous after- shock sequences are activated, that is, a minimum of 35% of the seismicity, similarly to tectonic seismicity. The observed decrease of the b-value with depth is also a property suggested for natural events. Our results suggest that the Aswan seismicity emerges both from the water-level loading and the interplay between induced earth- quakes themselves through numerous standard aftershock sequences. This latter pro- cess induces stochastic fluctuations in the seismicity patterns that inhibit a recovery of a simple seismic response to water-level changes. Even though aftershock se- quences dominate the temporal fluctuations of seismicity, this does not negate the importance of influence of the reservoir in sustaining this unusual long-lasting seis- mic episode. During the 1982-2001 period, the Aswan seismicity appears as a power- law relaxation response to the 1981 M 5.4 shock, this response being decorated by long-term (larger than 100 days) water-level changes.

Wetlands as Metabolic Gates

The wetlands and littoral flora of lakes and the land-water interface regions of rivers must be viewed as metabolic regulators of nutrient and organic matter loading to recipient waters. The interface communities of emergent and submersed macrophytes function as an integrated ecosystem of high organic productivity that supports intensive metabolism by attached microbial communities. The latter microbiota operate as an integrated community to conserve nutrients by intensive recycling. Nutrients imported via external loading are incorporated to support new microbial and plant growth within spatial and temporal constraints on community development. Nutrient excesses are exported downgradient. Organic matter released from the interface ecosystem is largely recalcitrant dissolved organic matter that is slowly degraded in recipient waters. An important variable of wetlands in the Great Lakes is marked, short-term changes in water level. These hydrodynamic oscillations modify loading rates of nutrients and organic matter from wetlands. Long-term water level changes can alter the extent and development of land-water interface regions. Hydrology of the ecosystem overrides metabolic capacities at high discharge, but often can be effectively managed to maximize system retentive capacities. Wetlands occupy a very small proportion of the drainage basins of the upper Great Lakes with deep, open pelagic waters. The regulatory influences of wetlands to nutrient loading and as a source of DOM increase in the lower Great Lakes but are relatively small in comparison to those of smaller inland waters.

Tide Gauge Records, Water Level Rise, and Subsidence in the Northern Gulf of Mexico

Long-term water level changes in the northern Gulf of Mexico were examined using tide gauge records for this century. Strong coherence exists between the annual mean water changes at Galveston, Texas, and (1) the relatively geologically-stable west coast of Florida, (2) global mean sea level, and 93) the subsiding Louisiana coast. Water levels at the Galveston gauge, one of the longest records (81 yr), have risen steadily, but not accelerated over the long-term. The apparent acceleration of water rise in the recent two decades is within the historical pattern, and is probably driven by regional or global, but not local climatic factors. Because eustatic sea level has risen steadily this century, the analysis supports the conclusion that regional geologic subsidence has not varied significantly over the tide gauge record (1909–1988). Variations in the estimates of subsidence in the surface layers are generally consistent with the generally accepted understanding of the geology of deltaic processes on this coast.

Anomalous water‐level changes and possible relation with earthquakes

Since late 1976 abandoned water wells have been monitored along the San Andreas and San Jacinto faults to detect water‐level changes which may be premonitory to earthquakes. An M5.5 earthquake occurred 25 February 1980 within the San Jacinto fault zone near Anza. The water level in a continuously recorded well in Borrego Valley 35 km from the epicenter rose 0.5 m and returned to its prior level during a four‐hour period beginning 88 hours before the earthquake. The water level in this well had been remarkably steady compared to other wells being monitored. Another well in Borrego Valley showed a much smaller rise and fall in water level at the same time. Because these changes are unique for the long‐term records of these wells, they may represent precursors to the earthquake.Several wells along the Palmdale‐Valyermo segment of the San Andreas fault showed possibly anomalous, long‐term water‐level changes which are not clearly related to rainfall. Between early 1979 and early 1980, water levels in six wells were .6 to 4.5 m higher and levels in two wells were about 3 m lower than would have been predicted based on the previous records. The water‐level increases could have been the result of delayed response to seasonal rainfall, following a long drought. However, it is interesting that the possibly anomalous water‐level changes first occurred at the same time as the reported changes in strain pattern from compression to expansion along the San Andreas fault in the same area.