Lars Bengtsson

Lund University | LU · Division of Water Resources Engineering

Cycling of water quality constituents in lakes is affected by thermal stratification and homo-thermal conditions and other factors such as oligotrophication, eutrophication, and microbial activities. In addition, hydrological variability can cause greater differences in water residence time and cycling of constituents in man-made lakes (res-ervoirs...

We assess the sustainability of rural electrification in Manica Province, Mozambique, focusing on different alternatives for mini-grid and off-grid power supply. The qualitative assessment considers four dimensions of sustainability, namely environmental , socio-cultural, economic, and institutional. We argue that small-scale hydropower is the most...

The consumption of oxygen in ice covered lakes is analyzed and related to biological oxygen demand and sediment oxygen demand. An approach for computing dissolved oxygen concentration is suggested assuming horizontally mixed waters and negligable vertical dispersion. It is found that the depletion of dissolved oxygen is mainly due to the transfer o...

Lake Titicaca is a crucial water resource in the central part of the Andean mountain range, and it is one of the lakes most affected by climate warming. Since surface evaporation explains most of the lake's water losses, reliable estimates are paramount to the prediction of global warming impacts on Lake Titicaca and to the region's water resource...

Lake Titicaca is an important water ecosystem of South America. Due to uncertainties in estimating the evaporation losses from the lake, surface water storage calculations are uncertain. In this paper, we try to improve evaporation loss estimations by comparing different methods to calculate daily and monthly evaporation from Lake Titicaca. These w...

Constructed wetlands have been increasingly used for treatment of secondary wastewater containing various contaminants. This paper presents a Variable Residence Time (VART)-based model, called VART-BOD model, for simulation of BOD removal processes in constructed wetlands with free water surface (FWS). Mathematically, the VART-BOD model describes a...

Observations of sea level and precipitation in Malmö, Sweden in the southeastern part of the sound Öresund have been used to estimate the probabilities of local compound events of high sea level and large daily and hourly rains. There are observations of sea level and daily rains extending back to 1930. The observations of short-term rainfall are f...

A procedure for evaluating depletion of snow covered area (SCA) using mean air temperature has been outlined and tested. Because depletion of snow is a cumulative effect of climatic conditions in and around snow cover area, the cumulative mean temperature (CTM) at a nearby station should represent deple- tion of SCA. The study was camed out for Sat...

Study region The study is carried out for Mumbai (18°58′30″ N, 72°49′33″ E). Study focus Future projections provided by general circulation models (GCMs) suggest the probability of occurrence of intense rainfall will change in the future. However, GCM data generally need to be downscaled and bias-corrected for impact studies. Although the domains...

Regional climate models (RCMs) are used for forecasting future climate including precipitation characteristics. Performances of five different RCMs for predicting the precipitation characteristics for Gothenburg, Sweden were evaluated against the daily observed precipitation over the period 1961 to 2009. Statistical analysis was done on annual, mon...

Daily rain series from southern Sweden with records dating back to the 1870s have been analysed to investigate the trends of daily and multi-day precipitation of different return periods with emphasis on the extremes. Probabilities of extreme storms were determined as continuously changing values based on 25 years of data. An extra set of data was...

Efficient design of urban drainage systems is based on statistical analysis of past rainfall events at fine time scales. However, fine time scale rainfall data are usually lacking in many parts of the world. A possible way forward is to develop methods to derive fine time scale rain intensities from daily observations. This paper applied cascade-ba...

The debate about dams is a debate about the very meaning, purpose, and pathways for achieving development. This suggests that decision-making on water and energy management should align itself with the emerging global commitment to sustainable human development and on the equitable distribution of costs and benefits. When the 45,000 large dams of t...

Very extreme events occur randomly in space and in time. In this paper daily precipitation from more than 200 stations within a 10 000 km 2 region in the very south of Sweden is analysed. While there is a relation between moderate daily precipitation and annual precipitation, the most extreme events are found to be independent of annual precipitati...

A method for reaching longitudinal dispersion coefficient accounting sinuosity effects is suggested. The proposed method was verified using 43 sets of measured field data from previous study were collected from 30 streams and these data were chosen depends on characteristics availability (flow parameters, fluid properties and Sinuosity). Statistica...

A method for reaching longitudinal dispersion coefficient accounting sinuosity effects is suggested. The proposed method was verified using 43 sets of measured field data from previous study were collected from 30 streams and these data were chosen depends on characteristics availability (flow parameters, fluid properties and Sinuosity). Statistica...

Urbanisation has burdened cities with many problems associated with growth and the physical environment. Some of the urban locations in India are becoming increasingly vulnerable to natural hazards related to precipitation and flooding. Thus it becomes increasingly important to study the characteristics of these events and their physical explanatio...

DefinitionCirculation is the water movement and mixing is the dispersion of particles. The circulation, as well as the dispersion in ice-free lakes is mainly caused by the wind. When a lake is ice covered, the wind does not act on the water surface, and the water movements are much determined by thermal processes and by the vertical movement of the...

DefinitionUrban snow is simply the snow in urban environments. Snow conditions in settlements and cities are different from those in the country side. Snow is removed by man. Activities within the city influence both the snow characteristics and its distribution, which are usually heterogeneous. The melt occurs at different rates at different place...

In this study, we respond to calls for further investigation on why and how scientists choose to commercialize their research. Mowery (University entrepreneurship and technology transfer: process design, and intellectual property, Elsevier, Oxford 2005), in his criticism of the US-system, emphasizes the need for multiple channels between university...

Short-term very intensive storms in the years 1980–2007 from rain gauges in Malmö have been analysed to find intensities of long return periods and to investigate trends. Observations from different stations have been pooled into series to which probability functions have been adjusted. Quality control of short-term precipitation records is emphasi...

Int. J. of Sustainable Water and Environmental Systems Volume 2, No. 2 (2011) 77-84 A method for reaching longitudinal dispersion coefficient accounting sinuosity effects is suggested. The proposed method was verified using 43 sets of measured field data from previous study were collected from 30 streams and these data were chosen depends on charac...

Integrated Water Resources Management (IWRM) is a relatively new approach in Bolivia. However, it is now generally accepted that this approach needs to be established in order to find sustainable solutions for development and is actively promoted by the Water Ministry, especially in environmentally fragile regions, such as the Lake Poopo basin. The...

Lake Poopó is a terminal lake of the Bolivian Altiplano, with high salinity and heavy anthropogenic pollution from centuries of extensive mining activity. This study aims to describe how the water quality of groundwater and surface water system in different subwater-sheds of the Lake Poopó varies with geology and hydrology. Measurements of total di...

Vegetated roofs are becoming a trend in urban design, among others as a tool for city greening, mitigating urban heat island effect, and lowering urban storm runoff. Additionally, pollutant removal within vegetated roofs is often expected; however, it is commonly not a design feature. This study investigated influence on runoff water quality from t...

A field study for the arid northwest China has been conducted to find water-saving strategies of drip irrigation for dense-planted crops. The annual water consumption for optimal growth was 420mm, of which soil evaporation was 27% and the foliage transpiration 73%. A relationship between soil water consumption and the irrigation amount, crop yield...

Differential heating of surface waters of lakes caused by shading from vegetation can induce convection, which could be significant for the ecosystem because the chemistry and biology can differ in the reed belt zone compared to the open lake. This process has been given little attention in the literature. In the present study surface currents just...

Vegetated roofs are becoming increasingly popular in urban environments. Still, several aspects of their influence on various urban infrastructures are not sufficiently investigated, including the roofs' influence on runoff water quality. In this study a first flush effect in runoff water from vegetated roofs during simulated artificial rain events...

Sediment resuspension can significantly affect the light climate and internal nutrient loading in shallow lakes. To predict wind-induced resuspension, a critical bottom shear stress or critical depth for the whole lake is typically used. It is suggested here that the availability of resuspendable material must also be considered and that this avail...

Lake Poopó in Bolivia is a large, extremely shallow lake. The lake surface area is ≈3000 km2 at its spill-over level, although it could dry out at times. The lake water level varies with the regional rains and with the water inflow from the Desaguadero River. This study focuses on using and comparing three different approaches to determine the hyps...

The relative influence a city has on river water quality depends on the land use within the river basin and the character of the basin. In this paper the small Höje River basin, typical for southern Sweden, is studied; the pollution loading from a number of sources is estimated and the effect of actions taken both in the city and outside on river w...

The fractional dispersion model for natural rivers, extended by including a first order reaction term, contains four parameters. In order to estimate these parameters a fractional Laplace transform-based method is developed in this paper. Based on 76 dye test data measured in natural streams, the new parameter estimation method shows that the fract...

The influence of extensive sedum-moss vegetated roofs on runoff water quality was studied for four full scale installations located in southern Sweden. The aim of the study was to ascertain whether the vegetated roof behaves as a sink or a source of pollutants and whether the age of a vegetated roof influences runoff quality. The runoff quality fro...

Lake Poopó, within the large Altiplano basin of Bolivia, is connected upstream to Lake Titicaca and downstream to the salares, the big salt fields. Small changes in precipitation and river inflows strongly affect the extent of the lake surface area. For times when there are no satellite images, it is difficult to determine the extent of the lake fr...

IntroductionMethodologyStudy BasinStudy Period and Data UsedResults and DiscussionsApplicationsConclusions References

For 10 consecutive winters, measurements were carried out in Lake Vendyurskoe, Karelia, Russia. The aim of these measurements was to investigate some of the physical processes in this small shallow lake during its ice-covered period. Detailed measurements of ice thickness and condition, snow thickness, water temperature, salt content, and currents...

This is a first attempt of a regional precipitation analysis over the Bolivian Altiplano. The study region is the semi-arid Poopó and Uru-Uru lake basin, in the southern tip of the Altiplano. Fifteen rain gauges and three wind stations are located within and around this basin were the source of data used to perform a regionalization of the precipit...

Precipitation and runoff data from several controlled experiments (with dry and wet initial conditions) on a Sedum album green-roof have been analysed by means of linear programming in order to estimate a unit hydrograph (UH). The obtained UH was able to accurately predict peak flows and runoff volumes for any rain input. Results from the experimen...

The runoff from real 3 cm thick sedum-moss roofs and from laboratory roof plots in southern Sweden is measured and analysed. Real rains and artificial storms are used for the analysis. The probability of high runoff is compared with the probability of high precipitation intensity. Intensity-duration-frequency curves for runoff are derived and it is...

The runoff from and the water balance of a thin extensive green roof with sedum-moss have been studied. The soil cover is about 3 cm underlain by a thin drainage layer. The water balance is determined on a monthly basis. The runoff from the green roof is much reduced compared to runoff from hard roofs because of evapotranspiration. The annual runof...

The impact of warmer climate on melt and evaporation was studied for rainfed, snowfed and glacierfed basins located in the western Himalayan region. Hydrological processes were simulated under current climatic conditions using a conceptual hydrological model, which accounts for the rainfall–runoff, evaporation losses, snow and glacier melt. After s...

The uptake of the heavy metals Cd, Zn, Pb, As, and Fe by aquatic plants — thereby entering the human food chain — was studied in the Poopó basin, located in the semiarid, central Andean highland of Bolivia. At twenty sites around Poopó and Uru-Uru lakes, samples of aquatic plants, sediments, surface water and groundwater were taken. The spatial dis...

The uptake of the heavy metals Cd, Zn, Pb, As, and Fe by aquatic plants — thereby entering the human food chain — was studied in the Poopó basin, located in the semiarid, central Andean highland of Bolivia. At twenty sites around Poopó and Uru-Uru lakes, samples of aquatic plants, sediments, surface water and groundwater were taken. The spatial dis...

The runoff from real 3 cm thick sedum-moss roofs and from laboratory roof plots in southern Sweden is measured and analysed. Real rains and artificial storms are used for the analysis. The probability of high runoff is compared with the probability of high precipitation intensity. Intensity –duration – frequency curves for runoff are derived and it...

Eco-roofs are becoming popular for aesthetic reasons and also as units of stormwater systems. It is thought that such roofs with soil cover and vegetation reduces the total runoff, the peak flows and improves the quality of the roof water. Here are reported investigations of runoff from thin, 3-4 cm soil, extensive green roofs with sedum-moss in so...

The present study sets out to investigate the sensitivity of water availability to climate change for a large western Himalayan river (the Satluj River basin with an area of 22 275 km2 and elevation range of 500 to 7000 m), which receives contributions from rain, snow and glacier melt runoff. About 65% of the basin area is covered with snow during...

Structural best management practices (BMPs) are now commonplace for stormwater management in new suburban developments; however, their installation in older central areas is limited. Here, the effect of disconnecting impervious areas from a combined sewer in favour of a new open stormwater system is investigated. The site, an inner city suburb of M...

Numerical schemes and stability criteria are developed for solution of the one-dimensional fractional advection-dispersion equation (FRADE) derived by revising Fick's first law. Employing 74 sets of dye test data measured on natural streams, it is found that the fractional order F of the partial differential operator acting on the dispersion term v...