Developing sustainable water management scenarios by using thorough hydrologic analysis and environmental criteria

Wetlands constitute a significant source of life since they incorporate unique habitats with endemic and migrant species. They also contribute to the preservation of high global biodiversity and they are under protection according to EU legislation. Nevertheless, during the last century, significant degradation has been observed in wetlands, mainly due to intensification of agriculture and poor water management practices. Calcareous fens habitat with the endangered species Cladium mariscus and Carex spp. is an ecologically significant wetland that undergoes great ecological stresses globally, due to the irrational use of water resources. In Trichonis lake, Western Greece, this habitat has been under deterioration during the last 50 years due to the lack of a sustainable water management plan that has caused destabilization of the hydrologic balance and high water level fluctuations. This human induced hydrologic regime has led to seasonal shifting between drought and flooding which constitute unfavorable conditions for this fen habitat and as a result significant elimination of this ecosystem extent has occurred. This study has adopted technologically advanced scientific methods such as GIS applications and remote sensing techniques to quantify the existing water resources and formulate a sustainable management scheme by considering both anthropogenic water uses and environmental protection.     

Long term changes in the eutrophication process in a shallow Mediterranean lake ecosystem of W. Greece: response after the reduction of external load

Lake Pamvotis is a shallow Mediterranean lake located in Western Greece near the city of Ioannina. The lake has been recognized as an internationally important conservation site under European Community legislation due to its rich biodiversity. However, during the last three decades the trophic status of the lake has changed as a result of anthropogenic activity (among others irrigation and domestic sewage discharge), resulting in serious problems. Here we present data about the long-term development in eutrophication of Lake Pamvotis. Water samples were collected and analyzed (water temperature, pH, dissolved oxygen, nutrients, chlorophyll-a) during three monitoring periods: 1985-1989, 1998-1999, 2004-2005. The high nutrient concentrations in the lake water during the three monitoring periods, as well as its eutrophic to hypertrophic status reflect the degree of impact anthropogenic activity has had on the lake. Commencement of a restoration plan in 1995-1996, involving sewage diversion, led to a reduction in external nutrient load and consequently to lower in-lake nutrients and Chlorophyll-a concentrations. Orthophosphate concentration decreased by about 87%, nitrates fell below 1.20mg/l, whilst the total reduction of inorganic N compounds showed a weaker downward trend, fluctuating between 0.39 and 1.24mg N/l with an average value of 0.76mg N/l. However, after a short-term recovery the eutrophic status of the lake remains eight years later (2004-2005), suggesting the importance of the internal loading process and the absence of the top-down effect of fish. This study provides evidence for the need of greater restoration efforts utilized in Mediterranean shallow lakes.     

Analysis of the recycling potential of used automotive oil filters using the Life Cycle Assessment approach

The aim of this study is to evaluate whether a specific recycling system for used oil filters (UOFs) is environmentally viable by considering all steps of the product's life cycle. In that aspect an analysis of the environmental impacts regarding different waste management scenarios of UOFs in Greece is presented using the Life Cycle Assessment (LCA) approach. Waste scenarios varied from maximum feasible recycling and recovery of metals and used lubricant oil, to disposal of UOFs to landfills without any prior treatment. In order to perform this analysis, the principles of ISO 14040 were followed and a relevant LCA software was used (SimaPro 7.2). Additionally, the results of a previous work conducted by the authors were deployed, including some experimental measurements undertaken so as to evaluate and quantify the factors affecting the recovery of the lubricant oil contained in used automotive filters. Indicatively, it was estimated that a maximum of 1340 tons of used oil and 1810 tons of steel are disposed every year in Greece, as a result of the non-effective management of used automotive filters.     

EFFECTS OF INSECTICIDE USE IN A PINE SEED ORCHARD ON PESTICIDE LEVELS IN FISH1

ABSTRACT: A hydroelectric lake on the Oconee River in central Georgia was sampled on a quarterly basis for four years to determine the impact of three insecticides on the pesticide loading of fish. The insecticides carbofuran (2,3,-dihydro-2,2-dimethyl-7-benzofuranyl methyl-carbamate), fenvalerate [cyano(3-phenoxyphenyl)methyl 4-chloro alpha (1-methylethyl)benzeneacetate], and azinphosmethyl [0,0-Dimethyl S-(4-oxo-1,2,3-benzotriazin-3-(4H)-ylmethyl phosphorodithioate] were used to control cone and seed insects on a pine seed orchard that is adjacent to Lake Oconee. Fish populations in areas of the lake that receive runoff from treated and untreated portions of the seed orchard were sampled using gill nets. Water and fish samples were collected monthly in 1981–1983 and quarterly in 1984. Species collected included carp (Cyprinus carpio), sucker (Catostomus spp., Erimyzon spp., Moxostoma spp., Minytrema spp.), bass (Micropterus spp.), channel catfish (Ictalurus punctatus), spotted gar (Lepisosteus spp.), and bluegill sunfish (Lepomis macrochirus). Few carbofuran residues (< 7 percent of fish samples contained detectable residues) and no azinphosmethyl or fenvalerate residues were detected despite measured inputs into the lake after insecticide application. Persistent agricultural insecticides including dieldrin, lindane, DDT, and toxaphene were detected in 32, 36, 58, and 83 percent of sampled fish, respectively. Screening for 20 other insecticides resulted in no detection of residues at a detection limit of 30–100 μg kg^-1.     

REMOTE MONITORING OF SELECTED GROUND‐WATER DOMINATED LAKES IN THE NEBRASKA SAND HILLS1

ABSTRACT: The Landsat‐Muitispectral Scanner (MSS) data were used to measure lake area fluctuations (1972–1989) for 130 ground‐water dominated lakes in the Western Lakes Region of the Nebraska Sand Hills. In general, the pattern shown in lake area hydrographs was similar to that for in‐situ lake elevations. In‐situ lake‐elevation data verify that remote monitoring of surface‐area fluctuations, even at relatively coarse spatial resolution, is not only practical and useful, but also it elucidates the hydrologic characteristics of groundwater‐dominated lakes of the Sand Hills. The apparent differences in behavior between lakes in the northern and southern portions of the study area may be related to both their location in the regional ground water system and the substantial local hydrologic complexity.     

A Drinking Water Crisis in Lake Taihu, China: Linkage to Climatic Variability and Lake Management

In late May, 2007, a drinking water crisis took place in Wuxi, Jiangsu Province, China, following a massive bloom of the toxin producing cyanobacteria Microcystis spp. in Lake Taihu, China’s third largest freshwater lake. Taihu was the city’s sole water supply, leaving approximately two million people without drinking water for at least a week. This cyanobacterial bloom event began two months earlier than previously documented for Microcystis blooms in Taihu. This was attributed to an unusually warm spring. The prevailing wind direction during this period caused the bloom to accumulate at the shoreline near the intake of the water plant. Water was diverted from the nearby Yangtze River in an effort to flush the lake of the bloom. However, this management action was counterproductive, because it produced a current which transported the bloom into the intake, exacerbating the drinking water contamination problem. The severity of this microcystin toxin containing bloom and the ensuing drinking water crisis were attributable to excessive nutrient enrichment; however, a multi-annual warming trend extended the bloom period and amplified its severity, and this was made worse by unanticipated negative impacts of water management. Long-term management must therefore consider both the human and climatic factors controlling these blooms and their impacts on water supply in this and other large lakes threatened by accelerating eutrophication.     

Environmental problems from practicing agriculture in Prespa National Park,Greece

Summary Prespa National Park is situated at the northwestern corner of Greece bordering Yugoslavia and Albania and covers 25,690 ha of which 8,114 ha are lake. The remaining area is forest, rangeland and arable land in the vicinity of twelve villages. The objectives of the park authority are to preserve the wetland with its special fauna of rare bird species, its flora, the geomorphological formations of the lake and the natural environment. The nucleus of the park is comprised by Lake Mikri Prespa and the surrounding wetland. It is in this wetland that an exceptional assemblage of rare and endangered species breed. However, the park is recently undergoing rapid development of its agroecosystems in terms both of higher subsidiary energy inputs, notably irrigation, and of acreage, i.e. of substituting some of the wetland for cropland. The objective of this study was to assess the potential environmental hazards from practicing agriculture in the park and to propose measures of abatement. Assessment was based on field surveys, administration documents and interviews. Cropland is not intensively used at present. Two thirds is covered by winter cereals and the remaining by other row crops (beans and potatoes). There are no deciduous orchards. Practices are carried out without regard for environmental conservation. Farmers' attitudes towards the wildlife range from indifference to hostility because they attribute the lag in their economic development to the past restrictions imposed by the National Park Administration. The main environmental consequences from the ongoing agricultural development in Prespa are assessed to be a dramatic increase of nonpoint agricultural pollution of the lake, with phosphorus and pesticides as the primary pollutants. Moreover, accidents in the use of pesticides may lead to immediate deterioration of the nucleus wildlife habitats. Since irrigated agroecosystems are there to stay and grow in subsidiary energy, measures are needed to prevent harmful consequences. Such measures are the alleviation of the land ownership problem, adoption of cultural practices to limit soil erosion, rational use of chemical fertilizers and pesticides and education of farmers. It is concluded that the internationally invaluable natural ecosystems of the park are definitely threatened by the development of the irrigated agroecosystems. The measures proposed will limit this threat and at the same time will help to perpetuate the productivity of the agroecosystems themselves.Mrs. M. D. Pyrovetsi is a lecturer in the Department of Biology and Professor P. A. Gerakis is Head of the Department of Agriculture; both are within the Aristotle University of Thessaloniki, Greece.     

Investigation of an Escherichia coli environmental benchmark for waterborne pathogens in agricultural watersheds in Canada

Canada's National Agri-Environmental Standards Initiative sought to develop an environmental benchmark for low-level waterborne pathogen occurrence in agricultural watersheds. A field study collected 902 water samples from 27 sites in four intensive agricultural watersheds across Canada from 2005 to 2007. Four of the sites were selected as reference sites away from livestock and human fecal pollution sources in each watershed. Water samples were analyzed for Campylobacter spp., Salmonella spp., Escherichia coli O157:H7, Cryptosporidium spp., Giardia spp., and the water quality indicator E. coli. The annual mean number of pathogen species was higher at agricultural sites (1.54 ± 0.07 species per water sample) than at reference sites (0.75 ± 0.14 species per water sample). The annual mean concentration of E. coli was also higher at agricultural sites (491 ± 96 colony-forming units [cfu] 100 mL(-1)) than at reference sites (53 ± 18 cfu 100 mL(-1)). The feasibility of adopting existing E. coli water quality guideline values as an environmental benchmark was assessed, but waterborne pathogens were detected at agricultural sites in 80% of water samples with low E. coli concentrations (<100 cfu 100 mL(-1)). Instead, an approach was developed based on using the natural background occurrence of pathogens at reference sites in agricultural watersheds to derive provisional environmental benchmarks for pathogens at agricultural sites. The environmental benchmarks that were derived were found to represent E. coli values lower than geometric mean values typically found in recreational water quality guidelines. Additional research is needed to investigate environmental benchmarks for waterborne pathogens within the context of the "One World, One Health" perspective for protecting human, domestic animal, and wildlife health.     

Multivariate statistical characterization of water quality in Lake Lanier, Georgia, USA

Watershed monitoring programs depend on water quality characterization data collected for many parameters, at many times and places, and with limited resources. Our objective is to present a strategy that reduces the measured parameters, locations, and frequency without compromising the quality of the monitoring program. One year of twice-monthly (growing season) and monthly (dormant season) water quality data collected from 17 lake and 10 tributary sites are used in conjunction with multivariate statistical techniques to improve the utility of collected data by identifying key parameters and monitoring locations. Factor analysis shows that tributary water quality data consists of three components-stormwater runoff, municipal and industrial discharges, and ground water-which can be distinguished using total suspended solids, total dissolved solids, and alkalinity plus soluble reactive P, respectively. Lake water quality characterization is more ambiguous than tributary water quality characterization, but factor analysis indicates that anoxia associated with lake stratification is the largest source of lake water quality variation, followed by nutrient abundance, and finally by biomass abundance. Cluster analysis suggests that tributary and lake monitoring stations can be consolidated. Reducing the number of parameters and stations frees up resources for increased monitoring elsewhere.     

Lake eutrophication management modeling using dynamic programming

Lake eutrophication problems have received considerable attention in Taiwan, especially because they relate to the quality of drinking water. In this study, steady-state river water quality and lake eutrophication models are solved using dynamic programming algorithms to find the nutrient removal rates for eutrophication control during dry season. The kinetic cycle of chlorophyll-a, phosphorus and nitrogen for a complete-mixed lake is considered in the optimization framework. The Newton-iterative technique is adopted to solve the nonlinear equations for the steady-state lake eutrophication model. The optimization framework is applied to Cheng-Ching Lake in southern Taiwan. Several nutrient loading scenarios for eutrophication control are studied. Optimization results for nutrient removal rates and corresponding wastewater treatment capacities of each reach of the Kao-Ping River define the least cost approach to lake eutrophication control. A natural purification method, structural free water surface wetland, is also suggested to save more investment and improve river water quality at the same time.     

Bottomfast Ice Mapping and the Measurement of Ice Thickness on Tundra Lakes Using C‐Band Synthetic Aperture Radar Remote Sensing1

Abstract: Industrial activity in Canada’s north is increasing, placing demands on the use of water from lakes to build ice roads. Winter water withdrawal from these lakes has the potential to impact overwintering fish. Removal of water from small lakes can decrease oxygen and habitat available to fish. To address this issue, a protocol has been developed by the Department of Fisheries and Oceans outlining water withdrawal thresholds. Bathymetric surveys are the traditional method to determine lake depth, but are costly given the remoteness of northern lakes. This paper investigates the use of satellite C‐band synthetic aperture radar (SAR) remote sensing technology as a potential alternative or complement to traditional survey methods. Previous research has shown that a SAR can detect the transition from grounded to floating ice on lakes, or if a lake is completely frozen. Grounded ice has a dark signature while floating ice appears very bright in contrast. Similar results were observed for the datasets acquired in the study area. This suggests that lakes that freeze completely to the bottom can be identified using SAR. Such water bodies would not be viable fish overwintering habitat and can therefore be used as water sources without thresholds necessary. However, attempts to accurately calculate the depth of the ice at the grounded‐floating ice boundary using bathymetric profiles acquired in the summer and lake ice thickness measurements from a reference lake near Inuvik proved to be unreliable.     

基于流域视角的水环境综合治理规划研究——以江苏省淀山湖为例

以流域为单元进行水资源综合规划和管理是实现水环境改善的重要途径。本文以太湖流域第二大省界湖泊—淀山湖为例,在综合分析流域水环境质量基础上,利用GIS 分析工具划分流域治理片区并制定分区管控策略。根据流域所含骨干河流流向、骨干河流与淀山湖交汇特点、上中下游不同河段及镇域行政边界,将淀山湖流域分为吴淞江流域、千灯浦- 淀山湖流域、昆南湖荡流域、元荡湖荡流域、太浦河流域五大片区138 个子评价单元。通过水环境容量与压力两类空间叠加分析,构建形成污染重点减排区、污染综合治理区、产业绿色化提升区、生态环境保育区等四个类型区域,并提出差异化的产业准入和环境治理措施。本研究不仅为以流域为治理单元的水环境治理规划提供了较为可行的技术体系,而且为太湖流域水环境综合整治思路创新提供了可借鉴的案例。     

Modeling Water Quantity and Sulfate Concentrations in the Devils Lake Watershed Using Coupled SWAT and CE‐QUAL‐W2

Devils Lake is an endorheic lake in the Red River of the North basin in northeastern North Dakota. During the last two decades, the lake water level has risen by nearly 10 m, causing floods that have cost more than 1 billion USD in mitigation measures. Another increase of approximately 1.5 m in the lake water level would cause spillage into the Sheyenne River. To alleviate this potentially catastrophic spillage, two artificial outlets were constructed. However, the artificial drainage of water into the Sheyenne River raises water quality concerns because the Devils Lake water contains significantly higher concentrations of dissolved solids, particularly sulfate. In this study, the Soil and Water Assessment Tool (SWAT) was coupled with the CE‐QUAL‐W2 model to simulate both water balance and sulfate concentrations in the lake. The SWAT model performed well in simulating daily flow in tributaries with E_NS > 0.5 and |PBIAS| < 25%, and reproduced the lake water level with a root mean square error of 0.35 m for the study period from 1995 to 2014. The water temperature and sulfate concentrations simulated by CE‐QUAL‐W2 for the lake are in general agreement with the field observations. The model results show that the operation of the two outlets since August 2005 has lowered the lake level by 0.70 m. Furthermore, the models show pumping water from the two outlets raises sulfate concentrations in the Sheyenne River from ~100 to >500 mg/L. Editor's note : This paper is part of the featured series on SWAT Applications for Emerging Hydrologic and Water Quality Challenges. See the February 2017 issue for the introduction and background to the series.     

Nutrient fluxes in a eutrophic coastal Louisiana freshwater lake

Nitrogen and phosphorus cycling in a eutrophic Louisiana freshwater lake system (Lac des Allemands) was studied. Nutrients from runoff entering the lake, as well as sediment-interstitial and lake water nitrogen and phosphorus fractions, were measured seasonally. Sedimentation rates in the lake were determined using¹³⁷Cs dating.Phosphorus levels in the lake were found to be largely dependent on concentrations in the incoming bayou water from upland drainage. Lake water concentrations appear to respond to fluctuations in incoming waters. Laboratory equilibrium studies showed bottom sediments in the lake are a major sink for the incoming dissolved orthophosphate phosphorus. Total nitrogen concentrations in the lake water generally exceeded incoming runoff concentrations, suggesting fixation by the large blue-green algae population in the lake as being the major source of nitrogen to the system.Sedimentation ranged from 0.44 cm/year to 0.81 cm/year, depending on the proximity to the inlet bayous. Even though the lake is eutrophic the sediment served as a buffer by removing large amounts of carbon, nitrogen, and phosphorus through sedimentation processes. Carbon, nitrogen, and phosphorus were accumulating in the sediment at rates of 60, 7.1, and 1.1 g/m²/year, respectively.The water quality of the lake is likely to continue to decline unless measures are taken to reduce municipal, industrial, and agricultural inputs of phosphorus into the lake.     

TEMPERATURE EFFECTS ON GREAT LAKES WATER BALANCE STUDIES1

ABSTRACT. Beginning of month water temperature profiles are estimated for each lake. These water temperature profiles along with surface water temperatures are used to determine the effects of thermal expansion and contraction of water on the net basin supply values obtained from water balance studies using end of month lake levels. It is demonstrated that net basin supply values (equivalent to precipitation on the lake minus the evaporation from the lake plus the runoff into the lake) obtained from water balance studies without accounting for the thermal expansion and contraction of water may be in error by as much as 100 percent during some months for each lake.     

Eutrophication of Lake Waters in China: Cost, Causes, and Control

Lake water eutrophication has become one of the most important factors impeding sustainable economic development in China. Knowledge of the current status of lake water eutrophicatoin and determination of its mechanism are prerequisites to devising a sound solution to the problem. Based on reviewing the literature, this paper elaborates on the evolutional process and current state of shallow inland lake water eutrophication in China. The mechanism of lake water eutrophication is explored from nutrient sources. In light of the identified mechanism strategies are proposed to control and tackle lake water eutrophication. This review reveals that water eutrophication in most lakes was initiated in the 1980s when the national economy underwent rapid development. At present, the problem of water eutrophication is still serious, with frequent occurrence of damaging algal blooms, which have disrupted the normal supply of drinking water in shore cities. Each destructive bloom caused a direct economic loss valued at billions of yuan. Nonpoint pollution sources, namely, waste discharge from agricultural fields and nutrients released from floor deposits, are identified as the two major sources of nitrogen and phosphorus. Therefore, all control and rehabilitation measures of lake water eutrophication should target these nutrient sources. Biological measures are recommended to rehabilitate eutrophied lake waters and restore the lake ecosystem in order to bring the problem under control.     

Use of Synthetic Aperture Radar for Selecting Alaskan Lakes for Winter Water Use1

Abstract: Water resources are limited in many areas of the North Slope, Alaska, particularly during winter. Water is used by the oil industry for ice road construction and maintenance, drilling and facility operations, and potable water supplies. The coastal plain between Teshekpuk Lake, in the National Petroleum Reserve‐Alaska (NPR‐A) and the Colville River has numerous shallow lakes, but further south in the northern foothills of the Brooks Range, and east to the Canning River, lakes are fewer. While many oil and gas lease sales have been conducted, or are proposed, access to the leases may be limited because of the lack of available water for ice road construction. Ice roads are the main means by which exploration is conducted in the Arctic, putting a stress on freshwater bodies that do not freeze to the lakebed in winter. Lakes that do not freeze to the lakebed also serve as overwintering habitat for fish. The purpose of this paper is to report on the potential distribution of water bodies that may provide overwinter water in selected areas from Teshekpuk Lake to the Canning River. The project used synthetic aperture radar (SAR) imagery to search for the presence of water in lakes in March 2006. In the Kuparuk and Canning SAR images, 52 and 61% of lakes were frozen to their beds by March 2006, accounting for 49 and 57% of the lake area in these study regions. Conversely, only 2% of the lakes in the Teshekpuk region were frozen to the bottom by March 2006. Unfrozen water was more available because of deeper and more numerous lakes in the Teshekpuk Lake region (west) than in the Canning River area (east). While only specific SAR tiles were analyzed herein, the method will be a useful tool for land managers who seek to evaluate the potential for ice road construction across the Arctic.     

LONG-TERM RECONSTRUCTION OF WATER LEVEL CHANGES FOR LAKE ATHABASCA BY ANALYSIS OF TREE RINGS1

ABSTRACT: The fact that dendrochronology can be a useful tool in water resources management is demonstrated by a study of past changes in lake levels. The study was necessitated by the recent (1967) closure of the gates on the W.A.C. Bennett Dam on the Peace River in British Columbia, causing a drop in water levels of Lake Athabasca, the lake levels control water level undulations in a series of smaller lakes which lie in the 1.5 million acre delta area along its western edge in Alberta. The W.A.C. Bennett Dam has by its regulation of the Peace River affected the river's historical role of creating a hydraulic dam during early summer flood stages thereby preventing outflow from Lake Athabasca and inducing annual inundation of the delta area. Because the ecololgy of the lake and adjacent delta region has depended on the now attenuated snow-melt flooding from the Upper Peace River Basin, it became necessary to consider some means of artificially inducing this annual inundation. It was not known, however, what the long-term water level changes were around which the present ecology had developed. Continuous historical lake level records exist only for the period 1935–1967. Was this period one of anomalously high or low water levels? Relatively old white spruce trees growing along natural levees of the channels in the delta region were found to contain tree-ring records that reflected the water stages in the channels. Because the water levels in the channels could be correlated with lake levels, it was possible to use the three-ring series to extend the known 33-year record of lake level changes to 158 years. By using canonical analysis and 10-day mean lake levels for three different subperiods in the 33-year period of calibration, along with tree-ring series from appropriately chosen stands of white spruce, reconstructions were made of the long-term record for late May, early July, and late September. The reconstructed record shows that the May 21–30 lake levels have been three times as variable in the past as in the period of historical record (1935–1967), the July 11–20 levels twice as variable, and the September 21–30 levels 10% less variable. However, the mean water level for each of the three subperiods for the long-term record is very close to the means for the period of historical record. The reconstructed record shows that, before the dam gates were closed, there was only one three-year period (1866–1868) in which the lake levels were as low as they have been since closure of the gates (that is, 1967–1970). (Levels were nearly as low, however, during the period 1942–1945.     

Lake Temperature and Ice Cover Regimes in the Alaskan Subarctic and Arctic: Integrated Monitoring,Remote Sensing,and Modeling1

Arp, C.D., B.M. Jones, M. Whitman, A. Larsen, and F.E. Urban, 2010. Lake Temperature and Ice Cover Regimes in the Alaskan Subarctic and Arctic: Integrated Monitoring, Remote Sensing, and Modeling. Journal of the American Water Resources Association (JAWRA) 46(4): 777-791. DOI: 10.1111/j.1752-1688.2010.00451.x Abstract: Lake surface regimes are fundamental attributes of lake ecosystems and their interaction with the land and atmosphere. High latitudes may be particularly sensitive to climate change, however, adequate baselines for these lakes are often lacking. In this study, we couple monitoring, remote sensing, and modeling techniques to generate baseline datasets of lake surface temperature and ice cover in the Alaskan Subarctic and Arctic. No detectable trends were observed during this study period, but a number of interesting patterns were noted among lakes and between regions. The largest Arctic lake was relatively unresponsive to air temperature, while the largest Subarctic lake was very responsive likely because it is fed by glacial runoff. Mean late summer water temperatures were higher than air temperatures with differences ranging from 1.7 to 5.4°C in Subarctic lakes and from 2.4 to 3.2°C in Arctic lakes. The warmest mean summer water temperature in both regions was in 2004, with the exception of Subarctic glacially fed lake that was highest in 2005. Ice-out timing had high coherence within regions and years, typically occurring in late May in Subarctic and in early-July in Arctic lakes. Ice-on timing was more dependent on lake size and depth, often varying among lakes within a region. Such analyses provide an important baseline of lake surface regimes at a time when there is increasing interest in high-latitude water ecosystems and resources during an uncertain climate future.     

Limnological effects of wood ash application to the subcatchments of boreal,humic lakes

To assess environmental risks of wood ash, limnological effects of ash application to the drainage basins of two small, humic lakes and one reference lake in southern Finland were examined in this three-year study. Treated areas corresponded to 12 and 19% of the total catchment and the amount of wood ash added was 6400 kg ha(-1). Immediate effects of wood ash on lake water were investigated in three tank experiments each lasting 1.5 wk. In tank experiments, addition of wood ash increased pH, alkalinity, conductivity, and Ca and P concentrations of humic lake water, while growth of phytoplankton decreased. After wood ash application to the subcatchments, pH, alkalinity, conductivity, and concentrations of K+, SO4(2-), and Cl- slightly increased, both in inflowing waters and in the lakes, but no increased leaching of Ca, N, or P from the treated subcatchments occurred. Phytoplankton biomass increased in both experimental lakes in comparison with the reference lake. In the lake with 19% application rate to the catchment, zooplankton biomass also increased. The results indicate that, over the short term, a small-scale ash treatment to a forested drainage basin will not necessarily cause significant changes in the water quality of boreal humic lakes, but at higher application rates, changes in water chemistry and biology are more evident.