Magnus Persson
Posts by Magnus Persson:
Hydrologiska aspekter på de höga europeiska elpriserna i augusti 2022
The electricity prices in Sweden and Europe during 2022 have reached very high levels. The main reason for this being the war in Ukraine, which has led to a decreased availability for gas. During summer, the electricity prices reached extreme levels when meteorological and hydrological factors worsened the situation on the electricity market. The highest daily electricity price on the Nordic market was reached August 30, when it was 462 €/MWh. In the present article we review how hydrological factors affected the electricity price in August 2022; drought, low water flow and high water temperature in European rivers.
Impact of extreme flows on bridges. A case study from Lagan river, Ljungby
Flowing water impacts bridges over rivers primarily in two ways: (1) hydrodynamic forces that directly impact the structure and (2) scouring at piers and abutments, including contraction scour. The design prin-ciples for bridges in Sweden, including both impacting forces and local scour, are relatively simplistic. The purpose of this paper is to examine the impact of extreme river flows on bridges, particularly in circumstances beyond the design flow, using as a case study Ljungby Municipality. Although the study was made with focus on Swedish conditions, the work is to a large extent based on international literature and experiences. First, an overview of the literature on the impacts of extreme river flows on bridges was conducted. This was followed by a numerical study using the HEC RAS (1D – steady flow) hydraulic model to simulate the impact of extreme flows on bridges in Ljungby. This resulted in inundation and flood hazard maps for the study area, besides the determination of overflowed bridges. A 100-year event resulted in the overflowing of the Ljungsätersbron. During the 200-year event, Ljungsätersbron and Söderbron overflowed. Also, abut-ment scour analyses were performed for all bridges. Overall, the modeling approach provided a satisfactory estimation of the potential threats posed by scouring at bridges abutments during extreme flow conditions.
Storage and transport of water under water
Placing water tanks or water pipes under water has the advantage that the walls are subjected to a much lower pressure difference. An underwater tank, where the walls are made from a flexible material like canvas, instead of metal or concrete, can adjust its volume to exactly the volume to be stored inside. Tennis tents are examples of such soft constructions on land. A pipe may economically assume a much larger diameter on the bottom of the sea, as compared to over land. That enables pipes with extremely low pressure drops and that the pipe also may be made of canvas. A common firehose is an example of such a pipe used on land – flat, transportable, cheap, and light when not used. Two examples for sweet water to drought-stricken Gotland are given. The first example is storing 1 million m³ from abundant-water- winters to summer, resulting in an annualised cost of 2 – 3 SEK/m³ ($0.2 – $0.3/m³). The other example is a 183 km long pipe in canvas transporting 2 m³/s sweet water to Gotland from mainland Sweden. That water is then roughly estimated to cost annually 1 SEK/m³ ($0.1/m³) used on Gotland. Could this be cheaper than desalination?
Kostnader vid anläggning, drift och underhåll av dagvattendammar
The need for knowledge about operation and maintenance of stormwater ponds increases as the number of stormwater ponds in the country increases and the ponds get older. It is partly about how ponds can be managed in a cost-effective way, partly how operation and maintenance efforts should be planned and how they affect the values (alt. ecosystem services) that a pond contributes. Knowledge of operation and maintenance is also a prerequisite for being able to design new sustainable facilities. As there are few studies on the subject, a study was initiated which aims to gain increased knowledge about operating and maintenance costs of stormwater ponds and to relate these to construction costs. By collecting informa-tion via interviews and document studies from 15 municipalities, it turned out that the total installation cost is 990/ m2 SEK. The cost of operation is 36–55,000 SEK/year, and maintenance costs of 320/ m2 SEK for trench dredging and 1,010/ m2 SEK for suction dredging. To be able to compare costs, a typical pond of 4000 m2 was created with a lifespan of 30 and 70 years, respectively. The calculations showed that the installation cost accounts for approximately 40–70% of the annual cost. It also turned out that with marginal extra costs during construction, you can reduce the total costs over a pond’s lifetime.
Kontroll- och byggledarhandboken VA
Municipal water and wastewater pipe projects are often complex in terms of quality assessment, work environment, technology, time frames, personnel resources, and budget frames. If the water and wastewater pipes laid today are to maintain the service life that the Swedish Water and Wastewater Association (Svenskt Vatten) sets as a goal, 100 – 150 years, it is important to carry out this type of projects systematically and with high technical quality. The main goal of the project was to assure that municipal water and wastewater pipe projects are built with the right quality to last the lifespan set as a goal by the Swedish Water and Wastewater Association. In order to assure quality in water and wastewater pipe projects water utilities, technical consultants, contractors, suppliers, and research institutes in the water and wastewater sector in Sweden have joined together and written a practical handbook, the ”Control and Construction Management Handbook for Water Utilities”. One of the most important conclusions of the project is that active follow up of control and construction management by the water utility as well as cooperation between the water utility and the contractor during the contract time is necessary in order to secure the long-term quality of water or wastewater pipe projects.
Transienter i VA-ledningsnät – en statusbedömning för VA-sverige
Unintentional or planned operations of valves and pumps create pressure waves, called transients, which travel through pipe systems with the risk of, among other things, breakage and fatigue. Knowledge about transients in pipes and associated effects are not new. The problems with transients in Sweden were elucidated in a report published in the 1980s, where several municipalities reported examples of pipe damage created by transients. With the aim of performing a follow up on the conclusions from this report, an overall survey was conducted to assess if problems and handling of transients have changed. The survey was carried out in the spring of 2021 and sent to seven of the larger water- and wastewater authorities in Sweden, where an assessment of the status on transient management was requested. For reasons of comparison, the survey contained similar questions as the survey from the 1980s. Results show that the problem with transients still exists for the authorities. Examples include injury among the operation staff, when hit by a valve detached from the piping system. Another example involves a flooded booster pumping station for fresh water. In total, all of the authorities provided examples of pipe bursts originating from transient events, indicating room for improvement. However, the authorities are familiar with the problem and stand positive to future cooperation in research and development projects within the field of transients.
Byggbar mark – hur utvalda aktörer värderar översvämningsrisk
Climate change is expected to increase the frequency of fluvial, pluvial, and coastal flooding which must be considered in spatial planning. More frequent floods will also affect financial stability by increasing the exposure of risk for insurance companies and creditors. This study investigates how selected stakeholders assess flood risk when planning for new development and protecting existing real estate. The study was per- formed through a literature review and semi-structured interviews with municipalities, county administrative boards, insurance companies, real creditors, authorities and interbranch organizations. When planning for new development, there are good possibilities to consider flood risk and the costs for protective measures can be shared with the developer. However, there are limitations in current legislation regarding the establishment of future protective measures. For protection of existing real estate, several stakeholders demand that the municipalities take greater responsibility. The municipalities have, however, no legal obligation for existing real estate and are hindered by the principle of equality in legislation, limited land authority and financing. Despite the increasing flood risks, the insurance companies’ strategy is to keep offering insurance, but the insurance coverage may need to be limited in the future. This study emphasizes that climate adaptation is a complex matter and that current legislation hinders the implementation of protection measures.
Hydrological modelling of a recycling facility with landfill
A parsimonious lumped model was developed for simulating a catchment composed of a landfill and recycling facility. The modelling results showed acceptable conformity with the observed values with NSE of 0.54 and R2 of 0.56 in hourly simulations, though the results were characterized by a general underestimation. The catchment model was coupled with a reservoir model to simulate the leachate storage ponds downstream of the catchment. The time simulated storage of the leachate ponds was aligning with the observed recordings with NSE of 0.96. Simulation of the expected climate change was made to deduce the required expansion of the ponds in future climate and the required additional volumes were calculated to 7,800 m3 for the current climate to avoid overflow, with 9,100 m3 for the near term and 10,100 m3 for the mid- and long-term effects of climate change. It is also recommended to optimize the leachate ponds storage by improving the treatment plant capacity, and/or by continuous control of inflow and outflow. An additional storage volume would probably still be needed.