Average Annual Water Level Research Articles

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.

Spatiotemporal Analysis and Trend Detection of Groundwater Levels Using Gis Techniques in Nadia District of West Bengal, India

Abstract Groundwater (GW) resources are influenced by several factors like over exploitation, geological formation, climate etc. A long-term GW level trend detection is necessary for sustainable groundwater usage planning in future. In the present study, long-term (1990-2013) spatio-temporal analysis of GW levels during pre-monsoon and post-monsoon was done to elucidate the GW level variation trends in Nadia. Results show that the groundwater levels dropped more than 2.5 m below ground level (bgl) in the central part of the district, however, this drop was less than 2.5 m (bgl) in the northern and southern part of the district. According to pre- and post-monsoon data, the average annual water level decreased beyond 3 m (bgl) in blocks of Tehatta II, Chapra and Chakdah. Average GW level at Krishnaganj and Chakdah, in pre-monsoon were 6.84 m (bgl) and 7.55 m (bgl) respectively, which was higher than the post-monsoon (4.20 m (bgl) and 4.43 m (bgl)). During post-monsoon except Karimpur-I, Krisnaganj (both negative trend) and Hashkali (no trend) and in pre-monsoon except Krisnaganj (negative trend) and Hashkali (no trend), all the other blocks had positive trend. The study reveals that the groundwater levels in the southeastern and northeastern regions of the district drops by more than 5 m bgl in pre-monsoon and more than 4 m bgl in post-monsoon. Such fluctuations of groundwater levels may have serious bearing on agricultural operations in this intensively cultivated and irrigated area.

УРОВЕННЫЙ РЕЖИМ ТРЕХ КРУПНЕЙШИХ ОЗЕР ЕВРОПЫ: ПРОШЛОЕ И НАСТОЯЩЕЕ

The largest lakes in Europe, as well as all water objects in the region, are under the influence of climate change. The most pronounced changes in the water regime of lakes are noted in the intra-annual distribution of the water level. The increase in the average annual air temperature (by 1.3℃ on average) and annual precipitation layers (from 35 to 77 mm/year on average) in the second climatic period practically did not affect the average annual water levels of lakes Ladoga and Peipus, whereas the average annual water level of Lake Onega in the second climatic period (1991 – 2020) increased by 10% compared to the first period (1961 – 1990). At the same time, the inflow to Lake Onega has not changed and is about 16.7 km3/year. For more than 140 years, there have been pronounced trends toward a decrease in the average annual water level of Peipus and Ladoga and toward an increase in the average annual water level of Onega. For the significance level =0.1, the trends of changes in the levels of the studied lakes are significant. The increase in the level of Onega is explained by the fact that this lake is under the influence of the Verkhne-Svirskaya HPP and is characterized by a retaining regime. The influence of the retaining regime also determined the heterogeneity of the average annual water levels of Lake Onega. In addition, the relative proximity of this reservoir to the White Sea results in a more pronounced influence of the Arctic air mass transfer on the conditions for the formation of runoff in the Onega catchment.

Разработка концептуальной схемы прогнозно-аналитической модели заболеваемости лихорадкой западного Нила на основе оценки природно-климатических факторов (на примере Волгоградской области)

The present study focuses on weather and climatic factors influencing the incidence of West Nile fever (WNF) in the Vol-gograd region. We aimed to describe a relationship between these factors and the WNF incidence and to create a conceptual scheme of a predictive-analytical model for making forecasts how an epidemiological situation would develop in future. According to this aim, we selected an approach that involved identifying a statistical correlation between the analyzed factors and the WNF incidence in the Volgograd region and estimating the power of this correlation. The study primarily relied on using correlation analysis that was followed by assessing authenticity of the study results. The obtained data made it possible to establish that air temperature was a leading potentiating factor in the Volgograd region. It produced certain effects that varied in their intensity on a whole set of abiotic and biotic factors (water level and temperature, numbers and activity of carriers, how fast the virus amplifies in carriers, etc.). The study established that use of comprehensive statistical data (average monthly indicators) allowed more precise esti-mation of correlations. We also considered and confirmed a hypothesis about a delayed effect produced by air temperature on population incidence and numbers of West Nile virus carriers in the Volgograd region; it was the most apparent in years with the maximum numbers of infected people (1999, 2010, and 2012). We revealed a statistical correlation between air temperature and average annual water level and the WNF incidence among population and the number of West Nile virus carriers. There was a strong correlation between the number of carriers and the WNF incidence. A conceptual scheme of a predictive model for determining rate of the WHF incidence in Volgograd region was created based on the statistical analysis results.

A conceptual scheme of a predictive-analytical model for describing incidence of west nile fever based on weather and climate estimation (exemplified by the Volgograd region)

The present study focuses on weather and climatic factors influencing the incidence of West Nile fever (WNF) in the Vol-gograd region. We aimed to describe a relationship between these factors and the WNF incidence and to create a conceptual scheme of a predictive-analytical model for making forecasts how an epidemiological situation would develop in future. According to this aim, we selected an approach that involved identifying a statistical correlation between the analyzed factors and the WNF incidence in the Volgograd region and estimating the power of this correlation. The study primarily relied on using correlation analysis that was followed by assessing authenticity of the study results. The obtained data made it possible to establish that air temperature was a leading potentiating factor in the Volgograd region. It produced certain effects that varied in their intensity on a whole set of abiotic and biotic factors (water level and temperature, numbers and activity of carriers, how fast the virus amplifies in carriers, etc.). The study established that use of comprehensive statistical data (average monthly indicators) allowed more precise esti-mation of correlations. We also considered and confirmed a hypothesis about a delayed effect produced by air temperature on population incidence and numbers of West Nile virus carriers in the Volgograd region; it was the most apparent in years with the maximum numbers of infected people (1999, 2010, and 2012). We revealed a statistical correlation between air temperature and average annual water level and the WNF incidence among population and the number of West Nile virus carriers. There was a strong correlation between the number of carriers and the WNF incidence. A conceptual scheme of a predictive model for determining rate of the WHF incidence in Volgograd region was created based on the statistical analysis results.

Future rise of the Great Lakes water levels under climate change

The Great Lakes of North America are the largest unfrozen surface freshwater system in the world and many ecosystems, industries, and coastal processes are sensitive to the changes in their water levels. The water levels of the Great Lakes are primarily governed by the net basin supplies (NBS) of each lake which are the sum of over-lake precipitation and basin runoff minus lake evaporation. Recent studies projected the future NBS of the Great Lakes by dynamically downscaling General Circulation Models (GCMs) using Regional Climate Models (RCMs). However, their RCMs had been coupled to one-dimensional (1D) lake column models which lack the ability to accurately simulate the Great Lakes’ hydrodynamics and thermal structure. In this study, an ensemble of three dynamical downscalings based on the Great Lakes-Atmosphere Regional Model (GLARM) is used to project the future NBS and water level of the Great Lakes. GLARM is a three-dimensional (3D) regional climate modeling system for the Great Lakes region that two-way couples an RCM to a 3D hydrodynamic lake and ice model, making this the first study to use such an advanced model for water level projection of the Great Lakes. For the present-day climate, over-lake precipitation and lake evaporation simulated by GLARM, along with the basin runoff simulated by the GLARM-driven Large Basin Runoff Model (LBRM), track the mean seasonal cycle of the NBS components remarkably well. In particular, compared to previous studies, the most significant improvements are made in estimating the lake evaporation. For future hydroclimate, the ensemble average projects an increase in annual NBS and average annual water level for each lake. The projected NBS increase is mostly due to an increase in over-lake precipitation and basin runoff combined with a relatively smaller increase in lake evaporation. According to the ensemble average, by 2040–2049, the average annual water levels of Lake Superior, Michigan-Huron, and Erie are projected to increase by +0.19, +0.44, and +0.28 m, respectively, relative to 2010–2019. The individual downscaling cases highlight the uncertainty in climate projection, showing both increases and decreases in annual NBS and water level projection. The projected changes in the average annual water levels by 2040–2049 relative to 2010–2019 range from −0.01 to +0.32 m in Lake Superior, −0.13 to +0.80 m in Lake Michigan-Huron and −0.09 to +0.54 m in Lake Erie.

Quantitative assessment of water level regime alterations during 1959–2016 caused by Three Gorges Reservoir in the Dongting Lake, China

Abstract Water level is considered as the key factor affecting the structure and function of lake ecosystems. The Mann-Kendall technique and range of variability approach (RVA) were used to quantitatively evaluate the hydrologic alteration due to Three Gorges Reservoir (TGR) in Dongting Lake. Results indicate the following. (1) The average annual water levels at Chenglingji station showed increasing trends (p < 0.05), while that at Nanzui station showed a decreasing trend (p < 0.05). The turning year occurred in 2003, which reflects the significant effects of the TGR on the water level regime. (2) The highly altered parameters were 1-, 3-, and 7-day minimum water levels both at Chenglingji and Yangliutan, and in October both at Nanzui and Yangliutan, with the degree of hydrologic alteration being larger than 80%. However, 1-, 3-, 7-, and 30-day maximum water levels at three stations had relatively small alteration, with the degree of hydrologic alteration being smaller than 41%. (3) The hydrologic alteration degrees at Chenglingji, Nanzui and Yangliutan station were all moderate, with changes of 50, 46 and 49%, respectively. (4) Water level regimes at Dongting Lake were mainly jointly affected by reservoir operation, land utilization change and river channelization. These changes in water level regimes have a negative impact on aquatic and terrestrial ecosystems. This study provides a scientific reference for the protection of lake ecosystems under hydrologic alteration.

Population Dynamics of the Bream Abramis brama in Lake Peipus

Population dynamics of the bream Abramis brama in lakes Peipsi and Pihkva for the period from 1980 to 2009 has been studied by means of cohort models. Bream stock increased steadily in Lake Pihkva until 1999 and in Lake Peipsi until 2004, however then a trend towards a decrease of stock down to the level of early 1980s has been detected. In the 2000s a decrease in the population average age has been registered; it could be explained by both an increase in fishing intensity and high recruitment rates of the late 1990s. Highly abundant bream generations emerged in both lakes simultaneously. In late 2000s low level of recruitment was noted in both lakes. The qualitative relationship between stock and recruitment is best described by Ricker’s curve. It has been shown that bream recruitment depends on water transparency, water temperature, average annual number of days with air temperature above 20°С, and average annual water level. The existing fishery pressure on the stock of bream is close to optimal. A further increase in fishing intensity in both lakes is impractical. The current level of equilibrium yield can be achieved with much lower fishing intensity.

The hydrological and water level data in Yom River basin of Thailand

Yom River basin located in Northern Thailand, faces perennial droughts and floods with great impact on agriculture and the economy in the surrounding landscape. Therefore, the purpose of the present study is to study the hydrological nature of the Yom River basin, by descriptive statistics analysis using daily water level data from four water level measurement stations, from April 1, 2007, to March 31, 2020. The lower part of Mae Nam Yom river is almost half of the Yom River basin area. The water allocation plan in 2019-2020 for six reservoirs suggests usable water of 116.5 million m 3 , with the water allocated at the beginning of the rainy season more than during the dry season. During the dry season most of the water was allocated for agriculture. In most areas of Yom River basin, there are droughts and floods happened not more than 3 times in the last 10 year. The daily water level data of all four water level measurement stations showed relatively clear seasonal variations. The daily water level peaked every hydrological year during the rainy season. The average annual water level was the highest in 2011 (258.92 ± 1.09, 183.26 ± 1.64, 145.56 ± 1.89, and 96.20 ± 2.17 m(MSL)), and the lowest in 2015, except at the Y.1C station in 2019 (258.01 ± 0.49, 182.10 ± 0.61, 144.01 ± 1.24, and 94.50 ± 0.56, m(MSL)). The average monthly water level started to rise since May, with its highest peak value is in September (259.67 ± 0.86, 184.27 ± 1.14, 146.21 ± 1.39, and 97.09 ± 1.57 m(MSL)). The average monthly water level is low from December to April (dry season), the lowest values are from February to March (257.82 ± 0.19, 181.65 ± 0.12, 143.91 ± 0.32, and 94.31 ± 0.20, m(MSL)).

Ecological water level and its safeguard measures in Lake Dongting

湖泊生态水位是维持湖泊生态系统健康的重要因素.基于洞庭湖城陵矶、杨柳潭、南咀3个水文站1959—2016年日平均水位序列进行分析，采用Mann-Kendall法、累积距平法和滑动T检验法综合确定洞庭湖水位变异时间节点，结合生态水位年内展布法以及IHA-RVA法，计算分析湖泊最小和适宜生态水位，并且采用Tennant法进行合理验证，在此基础上对水文变异前、后湖泊生态水位保障度进行研究.研究结果表明：（1）洞庭湖城陵矶和杨柳潭水文站年均水位呈上升趋势，而且城陵矶站水位上升趋势显著，南咀站年均水位呈显著下降趋势.（2）洞庭湖3个典型水文站水位年际变化突变年份为2003年，突变年份基本上与三峡工程蓄水时间相符.（3）城陵矶、南咀和杨柳潭年均最小生态水位分别为21.41、28.95和27.84 m，分别占多年平均水位的86.3%、95.9%和95.7%，城陵矶、南咀和杨柳潭年均适宜生态水位分别为23.29、29.51和28.36 m，分别占多年平均水位的93.9%、97.8%和97.5%，生态水位计算结果考虑了天然湖泊水位年内丰枯变化，满足了湖泊生态目标需求.（4）洞庭湖最低生态水位保障程度较高，基本能达到80%以上，但适宜生态水位保障程度相对较低，其中2003年以后洞庭湖10月和11月生态水位保障程度显著下降，与上游水利工程蓄水有关，建议在此期间采取调度措施适当增加洞庭湖水量，以保障湖泊生态系统的健康与生物多样性.;Lake ecological water level (EWL) is an important factor to maintain the health of lake ecosystem. Based on the analysis of the daily average water level series of Chenglingji, Yangliutan and Nanzui hydrological stations in Lake Dongting from 1959 to 2016, the hydrological variation characters of Lake Dongting were determined by Mann-Kendall method, cumulative anomaly method and sliding T test method. Based on the method of annual EWL distribution and the improved method of IHA-RVA, the minimum and optimal EWLs were calculated, and the Tennant method was used for the reasonability verification. Finally, the guaranteed rates before and after the abrupt point were analyzed. The results show that: (1) The average annual water level of Chenglingji and Yangliutan hydrology stations were both on the rise, with much significant trend for the former one. While the average annual water level of Nanzui station exhibited significant decline trend. (2) The time of abrupt changes in water levels of the three stations was 2003, which was basically consistent with the beginning operation time of the Three Gorges Dam. (3) The annual minimum EWLs of Chenglingji, Nanzui and Yangliutan stations were 21.41, 28.95 and 27.84 m, respectively, accounting for 86.3%, 95.9% and 95.7% of the multi-year average level. The optimal EWLs were 23.29, 29.51 and 28.36 m, respectively, accounting for 93.9%, 97.8% and 97.5% of the multi-year average level. Such defined EWLs could meet the requirements of lake ecosystem goals with the consideration on the annual changes in natural lakes. (4) the safeguarding on the minimum ecological water level in Lake Dongting is relatively high, basically reaching more than 80%, but the guarantee degree of the appropriate EWLs is relatively low. After 2003, the guarantee degree of Lake Dongting decreased significantly in October and November, which is related to water storage and conservancy projects in the upstream. The EWL guarantee measures in Lake Dongting were suggested to maintain the health and biodiversity of the lake ecosystem based on the low guarantee degree and the difference of annual EWL distribution.

Tree-ring reconstruction of the level of endorheic lakes in the south of West Siberia

The paper presents the dendrochronological method applied in reconstructing the changes in the water level of endorheic lakes from arid areas (on the example of two large endorheic lakes Kulundinskoye and Chany). Chronologies of annual ring width of Scots pine (Pinus sylvestris L.), growing in the pine belt forests in the south of West Siberia, were used as indicators of climate change. To obtain the longest reconstructions, we used the lengthen chronologies. For analysis, specimens of living trees and old wooden houses in the Altai Krai villages (adjacent to pine-belt forests) were used. Due to the dendrohydrological analysis, we have determined the relationship between the lake level and the radial pine growth. We have revealed a one-two-year lag in the response of hydrological objects to climate fluctuations. Correlation between the tree-ring chronologies and the average annual water level of Lake Kulundinskoye occurred more often due to proximity of both geosystems, i.e. the lake and pine-belt forests. At the same time, there was the best correlation for Lake Chany and the drysteppe chronology Uglovskoye 42_LL. In the course of investigations, we have extended the series for lakes Chany and Kulundinskoye up to 1584 and 1763, respectively. Spectral analysis of the series of the water level in both lakes allowed us to identify common cycles (i.e. 25-26, 40-46 and 80-100-year ones). For Lake Kulundinskoye, the 8 and 11-year cycles turned out to be the most significant. The analysis of secular cycles of hydrological series enabled to specify the trends in water-level changes of the studied lakes in the future.

DEVELOPMENT OF A HYDRO-STATISTICAL MODEL OF ESTABLISHING THE LIMITS OF STREAMS AND ITS VERIFICATION (ON THE EXAMPLE OF THE VYATKA-RIVER BASIN)

A new unique method for establishing the shoreline of watercourses has been offered. In accordance with the Russian Water code, the border of rivers and streams is the shoreline with a long-term average annual water level for the ice-free period. That level is unknown in advance: it cannot be directly measured afield; it is not given in hydrological directories, as it is not considered to be characteristic, and on cartographic materials the outlines of water bodies are given at the average water level for the summer-autumn low flow period. To determine the desired level, the authors proposed a new method using the example of the Vyatka River. The method is based on a hydrolytic statistical model: the predicted parameter is the value of ΔH (the excess of the long-term average water level for the ice-free period over the average level of the summer-autumn low flow period), and the predictors (factors) of the model are the conditions of flow formation and passage. These factors are connected with ΔH by a power dependence, which has coefficients established by the least squares method from observations at 17 hydrological stations. The average calculation error ΔH was 5.4 ± 2.2 cm (significance level 0.05). The equation allows for any point or segment of the watercourse to calculate the desired level, and then establish a shoreline using large-scale maps. In this case, hydrometric observations are not needed. Mapping of the shoreline of the Vyatka River within the Kirov city and comparison of its position with the shoreline on a detailed space image received on a date close to the calculated level show that the standard error of the planned coastal position does not exceed 1.3 m, which meets the requirements to the accuracy of land boundaries of the water fund.

Water level characteristics of Lake Caizi, lower reaches of the Yangtze River during wintering period based on long-term hydrological alteration

湖泊生态水位过程对维持湖泊生态系统结构、过程和功能的完整性具有重要意义，也是当今湖泊科学领域面临的重要科学问题.基于菜子湖湖区水位站（车富岭水位站）1956-2018年日水位资料，采用pettitt突变检验法分析水位的突变性特征.结合年保证率法得到菜子湖车富岭水位站低水位值，并在此基础上分析了低水位发生时间及历时、候鸟越冬期水位变化速率及其生态水位的区间阈值.主要结论有：菜子湖车富岭水位站1956-2018年年均水位无显著突变.菜子湖车富岭水位站低水位发生时间均值为年内的344 d，年际标准差为27 d，低水位的年均历时为69 d，标准差为49 d，有6年（1978、1997、2015-2018年）未发生低水位事件.菜子湖候鸟越冬期水位变化速率的均值为-0.009 m/d，年均值为-0.034~0.009 m/d，日均值为-0.051~0.016 m/d.菜子湖低水位发生时间的区间阈值为332~351 d，历时的区间阈值为33~98 d，变化速率的区间阈值为-0.070~0.020 m/d.加强菜子湖候鸟越冬期湿地生境保护适应性调度试验研究及生态环境监测，为菜子湖输水水位优化控制和菜子湖湿地生态保护提供科学依据.;The ecological water level process of lakes is of great significance for maintaining the integrity of the lake ecosystem structures, processes and functions, and is also an important scientific issue of lake science field nowadays. Based on the daily water level data, pettitt test was used to analyze the abrupt change characteristics of water level of Lake Caizi at Chefuling Station from 1956-2018. The low water level of Lake Caizi at Chefuling Station was obtained using the annual guaranteed frequency method. The starting time and duration of low water level, the water level change rate during the overwintering period of migratory birds and the interval threshold of ecological water level were analyzed accordingly. The main conclusions are as follows:there is no significant abrupt change point in the average annual water level of Lake Caizi at Chefuling Station from 1956 to 2018. The average occurrence time of low water level of Lake Caizi at Chefuling Stations is day 344, with the inter-annual standard deviation 27 days. The average duration time of annual low water level is 69 days with the standard deviation 49 days. Among the calculated 63 years, there are 6 years (1978, 1997, 2015-2018) without low water level event. The average rate of water level change during the overwintering period of migratory birds is -0.009 m/d, the annual average rate is -0.034-0.009 m/d, and the daily average rate is -0.051-0.016 m/d. The interval threshold of the occurrence of low water level of Lake Caizi is 332-351 d, the interval threshold of the duration time is 33-98 d, and the interval threshold of water level change rate is -0.070-0.020 m/d. Strengthening experimental study on habitat adaptation and ecological environment monitoring during the overwintering period of migratory birds to provide scientific basis for water level regulation and wetland protection of the Lake Caizi.

The World’s Largest Lakes Water Level Changes in the Context of Global Warming

The article is focused on the assessment of changes in the average annual water levels of large lakes of the planet in the changing climate conditions characteristic of the recent decades. Eight large lakes, i.e.Baikal, Balkhash, Superior, Issyk-Kul, Ladoga, Onega, Ontario, and Erie, located on the territory of Eurasia and North America, were chosen as the research objects. They were selected because of the availability of a long-term observations series of the water level. As is known, long-term changes in the lakes water level result from variation in the water volume. The latter depends on the ratios between the water balance components of the lake that have developed during a given year, which, in turn, reflect the climatic conditions of the respective years. The features of the water balance structure of the above-mentioned lakes and the intra-annual course of the water level are considered. The available long-term records of observational data on all selected lakes and their stations were divided into two periods: from 1960 to 1979 (the period of stationary climatic situation) and from 1980 to 2008 (the period of non-stationary climatic situation). The homogeneity and significance of trends in the long-term water level series of records have been estimated. It has been established that over the second period the nature and magnitude of the lakes water levels variations differ significantly. For lakes Balkhash, Issyk-Kul, Ladoga, Superior, and Erie, there is a general tendency for a decrease in water levels. For the remaining three lakes (Baikal, Onega, and Ontario), the opposite tendency has been noted: the levels of these lakes increased. Quantitatively, the range of changes in water levels on the lakes in question over the period of 1980-2008 ranged from -4 cm to +26 cm.

CHANGES IN PROSNA WATER LEVELS (BOGUSŁAW PROFILE) IN 1973-2017

The paper presents long-term changes in water levels of Prosna, one of the main rivers in Wielkopolska, i.e. the region which is widely regarded as one of the least abundant in water in Poland. It was established that during the last 40 years the average annual water levels of Prosny showed a downward trend at the level of 7.8 cm-dec-1 and were statistically significant at the level of p=0.05 and also p=0.01. In all months a decrease in the water level was noted, although it was statistically significant in seven cases. The highest decrease in average monthly water levels (statistically significant, p=0.05) occurred in August and December and progressed at a rate of 13.2 and 12.3 cm-dec-1. The consequence of the ongoing trend may be, among others, worsening of ichthyofauna living conditions or worse quality of Prosny's water.

Numerical modeling of exploitation and reinjection of the Guantao geothermal reservoir in Tanggu District, Tianjin, China

This paper establishes conceptual and mathematical models for the low-temperature Guantao geothermal reservoir (a study area of 533km2) in the District of Tanggu, Province of Tianjin, China. The models are developed using AUTOUGH2 code for production history. Pressure and temperature histories of 20 production wells were simulated, primarily by adjusting well productivity indices and the permeabilities of the various rock types. Good consistency was obtained between the measured and simulated pressure profiles. Pressure and temperature distributions of the Guantao reservoir were predicted for the production over the next five years, based on history matching simulations. The influence of different reinjection rates on reservoir pressure, temperature, and water level were studied. The results showed the average annual water level drawdown for the entire study area is 3.4m over five years. The average annual water level drawdown is projected to be 1.3m with 60% reinjection rate and 0.2m with 100% reinjection rate. The reinjection is based on the addition of a make-up wells which constitute a doublet with the existing production wells.Based on this observation, reservoir pressures and temperatures were further studied with doublet well distances ranging from 700m to 250m, for the injected separated water rate of (respectively) 60% and 100%. The results indicate that the pressure of production wells increased slightly with decreasing doublet well distances. A sensitivity analysis on the doublet-well distances showed that the distance between the reinjection and production wells should be greater than 500m to avoid thermal breakthrough.

Use of satellite data to assess the impacts of irrigation withdrawals on Upper Klamath Lake, Oregon

Abstract. Competition for scarce water resources in the Upper Klamath River Basin, Oregon has generated conflict among its stakeholders, as demonstrated by recent regulations on withdrawals from Upper Klamath Lake. Information on agricultural water usage can help assess the hydrologic impacts of irrigation and support operational decisions. This paper presents an experimental satellite-based evapotranspiration estimation system that is combined with the Variable Inflitration Capacity (VIC) hydrological model to estimate irrigation consumption, which is then used to assess the effects of irrigated agriculture on lake storage volumes and water levels. The hydrological model is calibrated with streamflow observations and used to estimate unmeasured lake inflows and guide water budget calculations. When combined with the VIC model, the satellite-based evapotranspiration estimation system shows that irrigation caused a decline of 0.3 m in average annual water levels and 0.5 m in mean October water levels, and an increase of 0.5 m in annual water level ranges at the lake from 2001 to 2005. The results demonstrate the potential of satellite data for agricultural water resource management at the regional scale.

The Age and Rate of Growth of the Sheepshead, Aplodinotus Grunniens Rafinesque, in the Upper Mississippi River Navigation Pools

This study is one of a series of studies made of the fisheries of the upper Mississippi River as part of the program of the Upper Mississippi River Conservation Committee. The scale method was validated for the species and growth rates were calculated. Latitude was not a factor in the growth of 902 sheepshead taken from navigation pools 4A, 8, 10, and 17. Growth rates within different areas of the same pool and from pool to pool were sufficiently alike so that the growth from Lake Pepin to Muscatine, Iowa, can be considered uniform. Sheepshead from the upper Mississippi River grow more rapidly than those of Lake Erie. Average growth for the first year was 4.9 inches followed by a 4.0 inch growth during the second year. At the end of the seventh year they had reached a total length of 18.1 inches, 2.3 inches longer than 7-year-old sheepshead from Lake Erie. Annual growth rates observed for the period 1939 through 1947 were 7.8 percent above the average in 1939 and 7.3 percent below average growth during 1945. No relationship existed between growth rates and average annual water levels. During the third year of growth 23 percent of the males reach maturity. The first mature females were observed during their fifth year. Growth rates of earliest maturing males and females were far above average. Management implications of these investigations of the sheepshead are (1) the uniformity of the growth pattern requires uniform regulations in the area studied and (2) maintenance of spawning stock is dependent on adequate survival of 16-inch females, the length at which more than 50 percent of the females are mature.