Annual Water Level Changes Research Articles

Deriving high-accuracy lake water-level changes from multi-source satellite datasets

ABSTRACT Satellite data have exhibited a great potential to track lake water-level changes. By integrating multi-source satellite datasets (i.e., Ice, Cloud and land Elevation Satellite-2 (ICESat-2) lidar datasets, Landsat imagery, and Global Surface Water Dataset (GSWD)), we proposed a method to track annual water-level changes of Lake Mead, USA over 1984–2018. Specifically, we first extracted ICESat-2 profiles as elevation information. Second, we used Landsat imagery to extract annual lake boundaries and calculate lake areas. Third, we constructed the relationship between elevations and inundation frequencies provided by the GSWD for ICESat-2 points, and applied it to extract annual water levels by using inundation frequency of Landsat derived lake boundaries. Finally, we created the relationship between lake water level and lake areas via a cubic polynomial model to refine the annual lake water levels. Our water level results agreed well with the in-situ data (R 2 = 0.99, p < 0.01, RMSE = 0.64 m). Our results showed that the ICESat-2 data performed well in providing accurate elevation information around the shore of lake. Using satellite datasets, our proposed method has the potential to derive water levels for water bodies worldwide in the future.

A dataset of lake level changes in China between 2002 and 2023 using multi-altimeter data

ABSTRACT Lake water levels are an important indicator of water balance and water cycles, and are essential for climate and environmental change studies and water resource evaluation. Currently, lake level measurements are scarce or inconsistent throughout the country, and traditional gauge measurements of many lakes are not feasible, so satellite altimetry is a vital alternative to gauge lake levels. However, the accuracy and sampling frequency of lake level time series are usually low because of time and space coverage limitations; therefore, it is necessary to utilize multi-altimeter data to monitor lake levels and obtain lake level changes over long time series. In this study, we extracted the water level changes in 988 lakes (>10 km2) in China between 2002 and 2023 based on ICESat/-2, Cryosat-2, Jason-1/2/3, and Sentinel-3A/3B altimetry data using waveform retracking, lake level extraction, lake level time series construction, the fusion of multi-altimeter lake level time series, and outlier removal. A total of 55% of the lakes in this dataset have been monitored for more than 10 years, and 34% have more than 12 times the annual average water level monitoring. At the same time, in situ data from 21 lakes were used for validation, and the average root mean square error (RMSE) for each of the datasets of ICESat/-2, Cryosat-2, Jason-1/2/3, and Sentinel-3A/3B versus the in situ lake levels are 0.223 m, 0.163 m, 0.207 m, 0.596 m, 0.295 m, 0.275 m, 0.243 m, and 0.317 m, respectively, and the mean RMSE of the fused lake levels reaches 0.332 m. During the monitoring period, the water levels in Chinese lakes generally increased. The overall annual average rate of change at the 20 and 10-year scales was 0.123 m/a and 0.151 m/a, respectively, among which the overall water levels in large lakes increased significantly. The lakes with a faster rate of decline in the water level were primarily small. The water storage in each lake region in China shows an upward trend, with the most significant increase in the Tibetan Plateau region, where the average annual water level change rate has remained above 0.15 m/a over the past two decades. This dataset has high spatiotemporal coverage and accuracy and can support the estimation of changes in lake water storage, analysis of lake level trends, plateau flooding, and the relationship between lake ecosystems and water resources.

Water level change of Lake Machang in eastern China over 1814–1902 CE

Abstract. Lake Machang, occupying an area of approximately 30 km2 in the city of Jining, eastern China, was a historical reservoir on the Grand Canal from the early 15th century to early 20th century. The premodern monthly water level observation of Lake Machang commenced in 1814 CE and ended in 1902 CE. The available observation data from the monthly records covered 75.6 % of the entire study period of 1814–1902. Although the water level was seemingly artificially influenced by human activities, monthly and annual water level changes still correlated well with precipitation. That is, climate is still the dominant factor in water level changes on seasonal and annual scales. The flooding of the Yellow River in 1871 carried a large amount of silt into Lake Machang, which resulted in the rise of the lake bed and reclamation initiated by local residents. After the reclamation activity was officially approved in 1900, Lake Machang was massively reclaimed and eventually dried up in the early 20th century.

三峡库区消落带重建植被下土壤微生物生物量碳氮含量特征

PDF HTML阅读 XML下载 导出引用 引用提醒 三峡库区消落带重建植被下土壤微生物生物量碳氮含量特征 DOI: 10.5846/stxb201610272191 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 重庆市林业重点科技攻关项目（渝林科研2016-8；2015-6）；国家国际科技合作专项（2015DFA90900）；中央财政林业科技推广示范项目（渝林科推[2014-10]）；重庆市研究生科研创新项目（CYS2015068）；重庆市研究生科研创新项目（CYB16066） Characteristics of soil microbial biomass C and N under revegetation in the hydro-fluctuation belt of the Three Gorges Reservoir Region Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为探究三峡库区消落带植被重建后，土壤微生物生物量含量特征及影响因素，对忠县消落带人工重建植被土壤及裸地土壤（作为对照）微生物生物量碳氮含量进行了调查研究。结果表明：（1）在消落带165-175 m高程土壤微生物生物量碳含量草地>林地>农耕地>裸地，微生物生物量氮含量规律与微生物生物量碳一致，农耕地明显提高；土壤微生物生物量总体呈现出草地最高、林地和农耕地次之，裸地最低的趋势，表明进行消落带植被恢复对土壤微生物生物量有显著的促进作用。（2）不同植被类型下，土壤微生物生物量碳氮比变化范围为8.02-10.25，土壤微生物生物量碳、氮占土壤有机碳、全氮的百分比范围分别是2.40%-4.60%和2.13%-3.58%，其中林地对土壤碳、氮库贡献显著高于裸地（P < 0.05）。（3）土壤微生物生物量碳、氮与土壤有机碳、全氮和pH值呈现显著相关性，与土壤含水量呈现极显著相关性，说明消落带重建植被土壤的这些理化性质对土壤微生物生物量碳、氮含量有强烈的影响。因此，在三峡库区消落带进行植被恢复重建能显著提高土壤微生物生物量及土壤质量，对加强三峡库岸生态系统的稳定性具有重要意义。 Abstract:Operation of the Three Gorges Dam Reservoir on the Yangtze River, China, has formed a hydro-fluctuation belt with an annual water level change of near 30 m spanning and an area of 350 km2. Such a change in water level has led to a direct shift in plant community composition within the hydro-fluctuation belt. Different vegetation types alter the riparian soil environment to varying extents, via their influence on the biogeochemical cycles of materials such as soil microbial biomass carbon and nitrogen. Accordingly, by determining the relationship between soil physicochemical properties and soil microbial biomass under different vegetation types, we can provide useful information for vegetation restoration in the hydro-fluctuation belt of the Three Gorges Reservoir Region. To explore the changes in re-vegetated soil quality in the hydro-fluctuation belt of the Three Gorges Reservoir, we examined the contents of soil microbial biomass carbon (SMBC) and soil microbial biomass nitrogen (SMBN) in this region. Soils under four typical vegetation types (natural grassland, artificial timber forest, crop land, and unplanted soil) were investigated in the reservoir riparian region of Zhong County (107°32'-108°14'E, 30°03'-30°35'N), located in the center of Chongqing Municipality. The results showed that both SMBC and SMBN content was the highest in natural grassland and the lowest in unplanted soil. Under different types of vegetation, the ratio of SMBC/SMBN ranged from 8.02 to 10.25, the ratio of SMBC/soil organic carbon (SOC) was 2.40%-4.60%, and the ratio of SMBN/total nitrogen (TN) was 2.13%-3.58%. The SMBC/SOC and SMBN/TN ratios of forest soils were significantly higher than those of the unplanted soil (both P < 0.05). Soil microbial biomass was significantly correlated with SOC, TN, and soil pH, and very significantly correlated with soil moisture. Our study showed that the physical and chemical properties of soil under revegetation had a significant impact on both SMBC and SMBN. Thus, revegetation facilitated an increase soil microbial biomass and enhanced soil quality in the hydro-fluctuation belt of the Three Gorges Reservoir Region. 参考文献 相似文献 引证文献

Use of MODIS satellite images for detailed lake morphometry: Application to basins with large water level fluctuations

Lake morphometry is essential for managing water resources and limnetic ecosystems. For reservoirs that receive high sediment loads, frequent morphometric mapping is necessary to define both the effective life of the reservoir and its water storage capacity for irrigation, power generation, flood control and domestic water supply. The current study presents a methodology for updating the digital depth model (DDM) of lakes and reservoirs with wide intra and interannual fluctuations of water levels using satellite remote sensing. A time series of Terra MODIS satellite images was used to map shorelines formed during the annual water level change cycle, and were validated with concurrent Landsat ETM+ satellite images. The shorelines were connected with in-situ observation of water levels and were treated as elevation contours to produce the DDM using spatial interpolation. The accuracy of the digitized shorelines is within the mapping accuracy of the satellite images, while the resulting DDM is validated using in-situ elevation measurements. Two versions of the DDM were produced to assess the influence of seasonal water fluctuation. Finally, the methodology was applied to Lake Kerkini (Greece) to produce an updated DDM, which was compared with the last available bathymetric survey (1991) and revealed changes in sediment distribution within the lake.

Analysis of transboundary Dojran Lake mean annual water level changes

Dojran Lake located in south-eastern part of the Balkan is shared by Macedonia and Greece. This valuable water body and its ecosystem are vulnerable both to climate and anthropogenic impacts. Within the period 1988–2002, the Dojran Lake water level decreased seriously (6 m) and the littoral zone of the lake became dry. This water level decline together with the simultaneous water quality deterioration resulted in a biodiversity diminish and plankton reduction. The attack on the ecosystem had a harmful impact on the economy in the region. In the last decade, the water increasing trend of the lake water level has been observed. How much the lake is impacted by natural climatic causes, and how much by human activities in the watershed, is a question that cannot be answered easily. The main obstacle for Dojran Lake sustainable water resources management is the fact that there is no exchange of data and information between Greece and Macedonia. Hydrological analysis is obtained using data measured for the period 1951–2010 at the meteorological and hydrological Nov Dojran gauging stations located on the Macedonian side. The aim of the paper is stimulation of a close international interdisciplinary monitoring and cooperation. Of crucial importance is to facilitate the free and unrestricted exchange of data and information, products and services in real and non-real time on matters relating to the safety and security of society, economic welfare and the protection of Dojran Lake environment.

A new time series vegetation–water index of phenological–hydrological trait across species and functional types for Poyang Lake wetland ecosystem

Despite the long history of vegetation mapping with remote sensing, challenges remain in effectively linking remote sensing observations with plant traits and environmental disturbance across species and functional types. This study proposes a classification of aquatic and wetland vegetation plant functional types (PFTs) using time series remotely sensed data applicable to wetland ecosystems with large annual water level changes like Poyang Lake, the largest freshwater lake–wetland of China. We first developed the aquatic and wetland PFT classification scheme which included perennial C4 grasses, perennial C3 reed, C3 (sedges and taller forbs), short C3 forbs, floating aquatic macrophytes, and submerged aquatic macrophytes. Using this scheme, time series normalized difference vegetation index (time series NDVI) images and time series vegetation–water index (time series VWI) images extracted from 32-m spatial resolution Beijing-1 microsatellite data were applied to perform two PFT classifications with a support vector machine (SVM) algorithm. We found that the time series NDVI-based SVM classification method mapped aquatic and wetland PFT distribution with an overall accuracy of 81.3%. However, when the information on water level fluctuation was combined with time series NDVI into a new time series index (referred to as time series VWI), the overall accuracy increased to 90.4%. Results suggest that time series VWI has a stronger capability in distinguishing wetland PFTs with different submersion times and flood tolerances than time series NDVI, and thus may be considered as a key input dataset for future PFT classifications in seasonally dynamic wetlands.

Historical water level change of Lake Weishan in East China from 1758–1902 AD: relationship with the flooding of the Yellow River

In order to understand high-resolution environmental changes, historical water level changes on decadal and centennial scales have been conventionally analyzed employing documentary records and lake sediments. However, annual records are still limited. Here we report the discovery of water level observations (up to monthly) in the historical literature of the Qing Dynasty (1644–1912 AD). We reconstruct the chronologies of annual mean, maximum and minimum water level changes of Lake Weishan from 1758–1902 AD. The chronologies are compared with the precipitation data (dryness/wetness index data) of four stations in the vicinity of Lake Weishan (i.e., Heze, Jinan, Linyi and Xuzhou). We suggest that the annual water level changes are related to the amount of precipitation at the four stations. In addition, the flooding of the Yellow River significantly affects Lake Weishan, always resulting in extremely high annual mean, maximum and minimum water levels in the lake. The flooding in 1871 and 1873 AD even destroyed the banks between Lake Weishan-Zhaoyang-Nanyang and Lake Dushan, thus forming a united lake. In particular, we identify a high water level interval from 1851–1855 AD, just prior to the Yellow River channel change event in 1855 AD.

Seasonal ecological changes and water level variations in the Sélingué Reservoir (Mali, West Africa)

This work investigates the ecological modifications induced by the annual water level change as a consequence of hydrological regime and power production in Sélingué, a monomictic reservoir in Mali (West Africa). High waters occur from November, after the flood, while low waters occur from June, at the end of the dry season. Decrease of water level is linked to environmental factors (marked hydrological pattern, both for river flow and rain) and to human management of the reservoir during the dry season (irrigation, high hydropower demand). Difference in elevation between the high water and the low water phases is 9 m. To assess the ecological impact of such water level variations, environmental and biological descriptors were studied on water sampled biweekly from November 2000 to November 2001 in stations representative of the north part of this water body. As a consequence of high water and of regional meteorology (NE trade winds), the water column in Sélingué is stratified from March to May. Stratification can act as a trap for nutrients in the hypolimnion, preventing the euphotic epilimnion to be realimented in dissolved P and N mineral components. This process lasts until the beginning of the monsoon (SW trade winds) when progressive warming and energetic inputs through storms allow vertical mixing. The sink-phase is then replaced by a spring-phase when the water column is not anymore stratified and when the water level is low enough to allow wind-induced resuspension and vertical mixing. At the end of the low water phase, phytoplankton blooms are observed, allowed by the proximity of the productive euphotic layer and the deep mineralization layer and their possible mixing. Water level is also important for fisheries, since fishes are “diluted” in high water (i.e., more difficult to catch with the artisanal tools operated by the local fishermen) but are “concentrated” in low water (i.e., more easily over fished in the minor riverbed, where most fishes are sheltered at the end of the dry season). Irrigation was until now a secondary purpose of the Sélingué project, behind power production. Sélingué is now of secondary importance for power production in Mali (behind Manantali) and the planned extension of irrigated areas in the Office du Niger is about to seriously increase the need of water from Sélingué, the only impoundment upstream. During a hydrological cycle, the only conditions possibly leading to ecological unbalance are met at the end of the low water period. As long as the water level is high enough to allow vertical stratification and vertical separation of the productive euphotic layer from the sink in the bottom layer, Sélingué trophic status varies from oligotrophy to mesotrophy. The low water phase is very sensitive, and wise management rules should limit its duration. But the projects leading to a more intensive and time-shifted use of Sélingué water could have as consequences an early dewatering of the reservoir and an early shift toward eutrophic conditions. Therefore, there is a need to define and to apply multipurpose rules of water level management that could help to minimize or to prevent these ecological consequences.