Catchment Area Characteristics Research Articles

Catchment Area Composition and Water Chemistry Heavily Affects Mercury Levels in Perch (Perca Fluviatilis L.) in Circumneutral Lakes

The environmental impact on the mercury level in perch (Perca fluviatilis L.) is examined using Partial Least Squareregression (PLS) on 48 environmental descriptors assessingland use, various catchment area and lake characteristics,lake water chemistry, and fish stock. The lake specificintercepts of Hg content vs. fish length regressions are usedto describe the Hg level in the fish. The Hg levels in perchfrom 78 circumneutral lakes were largely influenced by landuse in the surroundings. Boreal forest lakes had the highestHg burden in the fish, while fish from lakes heavilyinfluenced by arable land possessed lower contents. The Hglevels also showed a negative relationship to the concentrationsof dissolved ions and total nutrients in lake water, and to theperch growth rate, whereas the relationship was positive to theconcentration of TOC/humic matter. Lake pH did not have any significant influence on the Hg content in perch in these circumneutral lakes. The Hg levels in perch from lakes surrounded by large amounts of wetland were less satisfactorily explained by the presently examined environmental descriptors, which suggests that the Hg burden in fish from these lakes are influenced by other factors.

Linking space–time variability of river runoff and rainfall fields: a dynamic approach

Statistical self-similarity in the spatial and temporal variability of rainfall, river networks, and runoff processes has been observed in many empirical studies. To theoretically investigate the relationships between the various time and space scales of variability in rainfall and runoff process we propose a simplified, yet physically based model of a catchment–rainfall interaction. The channel network is presented as a random binary tree, having topological and hydraulic geometry properties typically observed in real river networks. The continuous rainfall model consists of individual storms separated by dry periods. Each given storm is disaggregated in space and time using the random cascade model. The flow routing is modelled by the network of topologically connected nonlinear reservoirs, each representing a link in the channel network. Running the model for many years of synthetic rainfall time series and a continuous water balance model we generate an output, in the form of continuous time series of water discharge in all links in the channel network. The main subject of study is the annual peak flow as a function of catchment area and various characteristics of rainfall. The model enables us to identify different physical processes responsible for the empirically observed scaling properties of peak flows.

Mercury content in roach ( Rutilus rutilus L.) in circumneutral lakes — effects of catchment area and water chemistry

The environmental influence on the mercury content in roach ( Rutilus rutilus L.) is investigated using partial least square regression on 46 environmental variables describing the land use in the catchment area, various catchment area and lake characteristics, lake water chemistry, and fish stock. The Hg content in the fish from the 78 investigated circumneutral lakes is heavily influenced by the land use in their surroundings. The boreal forest lakes possessed the highest Hg levels in roach, whereas fish from lakes surrounded by arable land had lower levels. The Hg levels also showed a negative relationship to the amount of dissolved ions and the total amount of nutrients in lake water. Lake pH did not have any significant influence on the Hg content in roach in these non-acidified lakes. The Hg levels in lakes influenced by large amounts of wetland were less well explained by the presently investigated environmental variables, which implies that the Hg burden in fish from this kind of lake is governed by other factors.

Methodology for design of water harvesting system for high rainfall areas

Although rainfall in high rainfall regions is sufficient to meet the water demand of crops, its spatial and temporal distribution makes rainfed farming a risky proposition. Water harvesting can reduce the risk substantially by facilitating early planting by taking maximum advantage of the rainfall, thereby insuring the crop against rainfall aberrations. The proper design of a water harvesting system in a high rainfall region should take into account the spatial and temporal behavior of rainfall, water requirement of the crops, in addition to catchment characteristics. A simulation model has been developed to design a system for determining catchment/command area ratio, size of tank, desirable command area of a single tank and the feasibility/economics of lining of tank. The methodology facilitating the design of the system considered the catchment area characteristics, command area, and efficiency of conveyance system. It was found that for a rice-based cropping system in eastern India, a catchment/command ratio of 3.0 and tank size of 1750 m 3/ha command area is required, which facilitates desirable moisture regime for rice and two irrigations to succeeding crop. The command area should not be extended beyond a limit to have a conveyance efficiency of 80% or more. Using traditional methodology, i.e. by total irrigation requirement method, the tank capacity requirement will be 4500–6000 m 3/ha command area.

URBAN LAND-USE INFLUENCES ON TRANSPORT OF HEAVY METALS TO LAKES AND CONCENTRATIONS IN FISH

To investigate the urban land-useinfluences on transport of heavy metals to lakesand metal concentrations in fish liver (perch andcrucian carp), ten lakes in the Stockholm havebeen investigated. The catchment areacharacteristics have been studied in detail andput on a GIS-platform. The morphometry, waterquality and sedimentological characteristics ofthe lakes have been mapped and the metalconcentrations in water, sediments and fish liveranalysed. Evidently, metal concentrations in fishdepend on many internal characteristics relatedto the lake food-web and predation pressure,water chemistry (which influences metalpartitioning coefficients and hence pelagic andbenthic metal transport pathways), and lakemorphometry and hydrodynamics (which influencetransport patterns and internal loading).However, many of these causal agents regulatingmetal concentrations in water, sediments andfish, depend on catchment area characteristics.One aim of this paper has been to quantitativelyrank how the studied factors influence metalconcentrations in lake water and fish usingstatistical methods to find out how much of thevariability among the lakes that can bestatistically explained by these factors. Thisshould provide an interesting base for furtherstudies on the role of other factors, notaccounted for in this study, and about causalmechanisms. The results may also, hopefully, beused to address questions related to remedialmeasures – what can actually be done to reducemetal transport from urban areas to lakes, andmetal concentrations in fish, and what can beexpected from such remedies? Normed catchmentheavy metal loads to the lakes have beencalculated from models. Two-step regressionmodels consisting of catchment ‘size’ andcatchment ‘urban status’ parameters could explainlarge parts of the variations in the metal fluxesamong the lakes. These two main clusters of catchment variables are defined and motivated in this work. Cu was found to be the metal most dependenton ‘urban status’ followed by Cr. Pb had aboutequal influences from the ‘size’ as from theurban catchment ‘status’ variables. Cd, Hg, Niand Zn were more influenced by the ‘size’ than bythe ‘urban status’. For most metals,concentrations in fish liver were found to bemost correlated to general urbanity parametersand Cu and Pb to communications variables.

Land use influence on 137Cs levels in perch ( Perca fluviatilis L.) and roach ( Rutilus rutilus L.)

The environmental influence on Chernobyl-derived 137Cs levels in perch ( Perca fluviatilis L.) and roach ( Rutilus rutilus L.) was revealed using partial least-squares regression (PLS). The 53 environmental predictors used describe land use in catchment areas, various catchment area and lake characteristics, lake water chemistry, and fish stock composition. The study showed a profound effect of land use on the 137Cs levels in fish. Radiocaesium deposited on arable land was retained in the soil to a greater extent than was 137Cs deposited on wetlands, which more easily leached out to the lake ecosystems. The 137Cs deposition close to the lakes had a more pronounced effect on 137Cs levels in the fish than did more distant deposition. The radiocaesium bioavailability is mainly governed by lake water cation content, as hardwater lakes had significantly lower 137Cs content in fish. Resuspension of 137Cs contaminated sediments only had a limited influence on the observed levels in fish.

Techniques for defining school catchment areas for comparison with census data

School performance tables have been used in the UK with the intention of giving parents an indication as to how well local schools are performing in order that they may make a more informed decision about which school to send their child to. It is likely that the performance measurements are not only a result of the success of the school but also dependent on the background of the children that attend it. School performance tables do not provide information upon the social context in which the school is set. It is, therefore, important to be able to provide information about the social characteristics of a school's catchment area. This is technically difficult because firstly school catchment areas are not strictly defined and secondly census units have no link to catchment geography of a school. This paper offers three techniques that may be suitable for establishing the link between the point information available on the performance of the school and the areal census data. Each technique is tested to see how well this link has been established in each case.

Frequency distributions and transformations of lake variables, catchment area and morphometric parameters in predictive regression models for small glacial lakes

There are more than 83 000 lakes in Sweden and about 81 000 of these can be characterized as small, glacial lakes. Similar proportions between small, glacial lakes and other lake types ought to exist also for lakes in other parts of the world influenced by the latest glaciation, e.g. North America, Russia and Finland. Most lakes on the earth belong to this population of lakes. All lakes from this population cannot be thoroughly investigated, only a sample of lakes. A key question then is: how will empirical models based on data from the sample of lakes predict for other lakes from the population? It is not possible to answer that question unless several sub-questions are first addressed. This work concerns one of those, does the frequency distribution of the sample represent the frequency distribution of the population? The work addresses this issue from the perspective of predictive empirical models for lake management and research. This work presents comprehensive data sets on a battery of practically useful standard lake variables from more than 900 lakes. All these lakes are Swedish, but they cover a wide range of geographical, geological and climatological characteristics and the results should be widely applicable for all lakes from this lake type. General recommendations on suitable transformations for empirical models are presented for 12 water variables (pH, total-P, colour, hardness, etc.), 13 catchment area characteristics (bedrocks, soils, etc.) and 17 lake morphometric features (size and form parameters). This paper also presents case studies demonstrating the importance of selecting the right transformations for predictive empirical models. New models for Secchi depth, lake pH, colour and total phosphorus are presented to illustrate the practical utility of the results concerning transformations. The effects of sample size on transformations choices are also evaluated.

Variations in price elasticities

Multilevel analyses have been performed on weekly scanner data obtained from 74 stores of a large retailing chain for 30 competing items of a household product group. Discrete price change parameters for the brand being modelled reflect the fact that prices do not change from week to week. Their estimates show that the price elasticity is not constant. Variance components models for four of the products suggest that a brand's inherent attractiveness is affected by the social and demographic characteristics of the retail outlet's catchment area. However, random slopes models indicate that there are no systematically different price effects between stores.

The turnover of cesium-137 within a forest ecosystem described by a compartment modelling approach ? Gide study site, Sweden

A new comprehensive data base including catchment area characteristics and information about radionuclides deposition, migration in soil and transport in groundwater within the catchment ‘Orrmyrbäcken’ has been studied when modelling the turnover of cesium-137 within the Gideå study site. The BIOPATH code (compartment technique) was used to describe the long-term transfer within the whole catchment area. The concentrations of cesium-137 in surface water and soil were used for evaluation of the model. The model describes the concentration in surface water quite well. The initial transfer to the water, during the time when the snow melted cannot be evaluated due to lack of observed data. One of the results, was that about 5% of the initially deposited cesium-137 had left the catchment area after 5 years. Uncertainty analysis has been performed to identify the importance of different parameters. The source term, i.e. the deposition, initially contributes most to the uncertainty of the concentration in surface water and groundwater as well as in soil and peat. Furthermore, the water turnover and Kd-values in soil will increase their importance with increasing time.

The turnover of cesium-137 within a forest ecosystem described by a compartment modelling approach — Gideå study site, Sweden

A new comprehensive data base including catchment area characteristics and information about radionuclides deposition, migration in soil and transport in groundwater within the catchment ‘Orrmyrbäcken’ has been studied when modelling the turnover of cesium-137 within the Gideå study site. The BIOPATH code (compartment technique) was used to describe the long-term transfer within the whole catchment area. The concentrations of cesium-137 in surface water and soil were used for evaluation of the model. The model describes the concentration in surface water quite well. The initial transfer to the water, during the time when the snow melted cannot be evaluated due to lack of observed data. One of the results, was that about 5% of the initially deposited cesium-137 had left the catchment area after 5 years. Uncertainty analysis has been performed to identify the importance of different parameters. The source term, i.e. the deposition, initially contributes most to the uncertainty of the concentration in surface water and groundwater as well as in soil and peat. Furthermore, the water turnover and K d-values in soil will increase their importance with increasing time.

Sensitivity of soils and waters to acidification, Finnish Lapland

This paper reports the preliminary results of an investigation into the effects of the geological characteristics of catchment areas on the sensitivity to acidification of small lakes in Finnish Lapland. The sensitivity of mineral soil to acidification becomes more apparent due to special geological features and the relatively harsh climate. The sensitivity to acidification of lakes strongly depends on the geochemical properties of soil in the catchment areas. The buffering capacity of the drainage and the headwater lakes exhibit a positive correlation with the sum of the base cation equivalents of mineral soil. According to the preliminary results the buffering capacity of closed lakes seem to have no correlation with the base cation contents of the catchment areas. The study was carried out as a co-operative effort of the Geological Survey of Finland and the Water and Environmental District Office of Lapland.

Joint Consideration of Combined Sewerage and Wastewater Treatment Plants

Wastewater treatment plants, combined sewerage, catchment areas, storage tanks and overflows have to be regarded together. Stormwater runoff results in discharges at combined sewer overflows and higher pollutant loads in the effluent of the treatment plants. Characteristics of catchment areas and sewerage, number and capacity of storage tanks and overflows determine the characteristics of the combined water influent of the treatment plant. The plant has to cope with a higher hydraulic load and often with higher pollutant loads at the beginning of combined water flows. Some of the effects are displacement of sludge to the secondary clarifier, higher solids concentrations in the effluent and high loads of ammonia nitrogen for the nitrifying reactor. To decide on bigger stormwater storages or improvement of the treatment plant all effects in the whole system have to be considered. This can only be done with dynamic models, although simulation of combined water flows still have to be improved.

Urban Drainage Strategies for Small Communities in Developing Countries

In this paper, the interactions of small waste water treatment plants within an urban drainage system are pointed out. Especially in developing countries, the characteristics of catchment areas differ very much from the ones in industrialized countries. Consequently, the plants have to be adapted to the local conditions of drainage, climate and location. Finally, an urban drainage strategy will give an idea how to sanitize drainage systems.

Evaluation of the nutritional status of 1st-year school children in Campinas, Brazil

We present findings from a study of nutritional status amongst 1st year primary school children in Brazil. The study was based on a 10% stratified random sample of children in Campinas, Sao Paulo State. The primary schools in the city were grouped into four socio-economic strata (high, medium, low and very low) based on the type of school maintenance (private or maintained by the local or by the State government) and the socio-economic characteristics of the school's catchment area. The nutritional status of 1942 children was assessed by looking at the distributions of z-scores of weight-for-age, height-for-age and weight-for-height in relation to growth charts of the National Center for Health Statistics reference population. In the overall population, 22% of the children were found to be stunted (z-score of height-for-age less than -1.0), 15% wasted (z-score of weight-for-height less than -1.0), 22% underweight (z-score of weight-for-age less than -1.0) and 5% overweight (z-score of weight-for-height greater than 2.0). These figures represent an excess of 6% of stunted children and also 6% of underweight children in comparison with the expected values in the NCHS reference population, and an excess of 2% overweight. The data were analysed by age, sex, ethnic group and socio-economic level. Both stunting and low weight-for-age were observed in 32% of children from the very low socio-economic level, with the highest percentages amongst the oldest children. A total of 11.6% of children from the high socio-economic stratum were obese. These results emphasize the need for different programmes to deal with nutritional problems in different groups of the population.

Surface Infiltration Characteristics of Urban Catchment Area

Surface Infiltration Characteristics of Urban Catchment Area

Social activism and Community Mental Health: A policy perspective

Staff at 20 Community Mental Health Centers drawn from a national base and representing a variety of organizational forms and catchment area characteristics were queried regarding the degree to which they endorsed various strategies to change the social structure in order to improve mental health. It was found that the tendency to endorse these strategies varied by the occupational affiliation and belief system of the worker and by organizational and catchment area characteristics of the CMHC. In the light of the report of the President's Commission on Mental Health, the implications of the findings for training programs and future community mental health initiatives are discussed.

Social activism and psychiatrists in community mental health centers.

A sample of psychiatrists (n = 72) working in 20 community mental health centers (CMHCs) representative of the organizational and catchment area characteristics of operating Centers were queried as part of a larger study (n = 595) of community mental health worker roles. It was found that psychiatrists were like other staff in perceived organizational expectations of social activism but were significantly lower in perceived personal/professional role activism and role discrepancy. Unlike other staff, psychiatrists' levels of activism and discrepancy were unaffected by personal characteristics or organizational and catchment area characteristics of the CMHCs. It was concluded that the psychiatrists' unwillingness to assume any but the most modest community activist stances may hinder the development of the CMHC movement.

The Community Mental Health Worker: Organizational and Personal Sources of Role Discrepancy

The development of the ideology of community mental health (CMH) as the raison d'etre of a new mental health care movement has not insured its application in community mental health centers (CMHC). In order to actualize this new ideology, the CMHC staffs were expected to assume new roles: change agents or social activists. If ideology is a prescription for general behavior, then the existence of appropriate role development is a measure of the ability to translate ideology into behavior. This research measures the role discrepancy and content of CMH workers (N = 595) in a nationwide sample of workers drawn from twenty CMHCs representing differing center organizations and catchment area characteristics. The role discrepancy is measured by the differences in extent of activism in the worker's personal! professional definition of the role and the worker's perception of the center's role prescription. Role and role discrepancy vary by the nature of the center, the worker's discipline (discrepancy and activism are particularly low for those with medical backgrounds), worker's community mental health ideology, and by worker's function within the center. Role discrepancy decreased by worker's age and years at center. The level of activism in centers and the level and heterogeneity of role discrepancy indicate that the attempt to translate the ideology into role may be divisive to the functioning of the centers and that the disagreements about how to treat mental illness are perpetuated in the centers.

Modèles d'étiage

The term "low-water flow" conveys a variety of meanings and ideas, which can, however, be summed up under two main headings ; 1) the extreme case or extreme conditions and 2) insufficient flow available to meet the demand. In addition, models are more especially suitable for 1) discharge prediction for the design of river structures and 2) discharge prediction (in the strict sense of the word) for flow management purposes. Among the models recently designed in France for the extreme case, the following merit closer attention;- (i) A model for the determination of the characteristic low water discharge, which offers the possibility of extending measured flow series by observed rainfall series (M. Roche). (ii) A regional model enabling the annual minimum of a mobile mean of given length to be estimated in terms of rainfall and catchment area characteristics (J. Dauty). (iii) A model for use in attempting to predict the minimum annual discharge (J. Bernier). Models designed to compare available supplies with requirements are based on the two following possible principles;- (i) Determination of discharge with respect to a given requirement level in order to be able to predict short-supply conditions (J. Astier). (ii) The construction of discharge models, which are then compared with the requirements, with the same object in view (J. R. Tiercelin). A discharge model has been developed for this purpose and a rainfall/ runoff model is now being prepared, to enable measured flow series to be extended by observed rainfall series, and in order to be able to allow for irrigation requirements.