Environmental tracers and indicators bringing together groundwater, surface water and groundwater-dependent ecosystems: importance of scale in choosing relevant tools

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Groundwater dependent ecosystems. Part I: Hydroecological status and trends

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Impact of hydropower regulation on river water geochemistry and hyporheic exchange

Hydropower regulation of rivers exhibits a threat to the riverine ecosystems. Fragmentation of flow, landscape disturbances, and water retention are key features of regulated catchments, resulting in reduced floods and geochemical tr¬ansport, non-natural water level fluctuations, and thus disturbed exchange between the river and the aquifer. Storing of water in reservoirs reduces peak flow and turbidity, which increases particle settling and sometimes favours enhanced primary production and formation of a clogging layer. This in turn alters the interaction between surface water and groundwater, with potential secondary effects on the entire watershed. In Scandinavia, only eight large rivers (16%) remain entirely unregulated. The Lule River, the primary focus of this study, belongs to the most regulated rivers of Eurasia with a degree of regulation (i.e. the volume of water that can be stored in the reservoirs and used for regulation) of 72%, and is exposed to both seasonal and short-time regulation.Using hydrogeochemical analysis of two adjacent boreal rivers (pristine Kalix and regulated Lule River) discharging into the Gulf of Bothnia, the effects of regulation on river geochemistry were investigated. For the Lule River, the average maximum runoff was almost halved while the average minimum runoff was tripled as a result of the regulation. The winter transport fraction of total organic carbon, Fe, Si, suspended Mn and P in the Lule River was at least two to three times higher than in the pristine river. During summer, the suspended C/N ratio in the regulated river was 10-20, compared to &lt;10 for the pristine river, suggesting a presence of predominantly decaying organic material due to longer residence times for the regulated river. This was supported by a virtually constant suspended P/Fe ratio throughout the year in the Lule River, indicating low abundance of phytoplankton. Hence, a pronounced impact on the ecosystem of the river, the hyporheic/riparian zone, and the Gulf of Bothnia is expected.In spite of vast anthropogenic pressure on riverine ecosystems, the knowledge regarding the hyporheic zone (the interface between rivers and aquifers where exchange between surface water and groundwater occurs) is limited for regulated rivers. Therefore, this study was extended to also cover the hyporheic exchange along the Lule River. Temporal changes in hyporheic fluxes across the river channel (rates and directions) were determined using seepage measurements and continuous observations of water stages, temperatures, and electrical conductivity for both the river and the groundwater. While the river water level changed frequently (typically twice a day with up to ± 0.5 m), the river remained gaining 90% of the time, and the largest number of observed changes in flow direction (observed at 5 m orthogonal distance from the river) was six times per week. Flow velocities ≤10-4 m d-1 ( zero flow) constituted 1.5% of the total observation time.Although no changes in water temperature were observed for the hyporheic zone, effects of river level variations were detected up to 5 m inland, where electrical conductivity occasionally decreased to surface water levels indicating infiltration of river water into the aquifer (negative fluxes). River discharge regulation may therefore have severe implications on biogeochemical processes and deteriorate the hydroecological functions of the hyporheic zone.Godkänd; 2013; 20130211 (dmysie); Tillkännagivande licentiatseminarium 2013-02-21 Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Dmytro Siergieiev Ämne: Tillämpad geologi/Applied Geology Uppsats: Impact of Hydropower Regulation on River Water Geochemistry and Hyporheic Exchange Examinator: Ass. Professor Angela Lundberg, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Diskutant: Professor Hjalmar Laudon, Inst. för skogens ekologi och skötsel, Umeå Tid: Fredag den 15 mars 2013 kl 13.00 Plats: F531 Bergsalen, Luleå tekniska universitet</p

Hydrogeochemical effects of hydropower regulation on river-aquifer continuum in boreal rivers

Hydropower infrastructure affects many large rivers worldwide, threatening riverine and coastal ecosystems by fragmenting flow, disturbing landscapes and water retention and altering sedimentation and primary production. This thesis investigated major impacts of hydropower regulation on hydrological and geochemical processes in large boreal rivers. Geochemical river transport, sediment composition and hydrogeochemical functioning of the river-aquifer interface were studied in the regulated Lule River and the unregulated, otherwise similar, Kalix River in Northern Sweden.Regulation halved mean maximum runoff and tripled minimum runoff and winter transport of total organic carbon (TOC), Fe, Si, suspended Mn and P compared with the unregulated river. Summer suspended C/N ratio was 10-20 and &lt;10 in the regulated and unregulated river, respectively, indicating organic matter decay during long residence times in Lule River reservoirs. Suspended P/Fe ratio varied little annually in the regulated river, indicating low abundance of phytoplankton. Sediment cores from the headwater reservoir revealed simultaneous Fe and P sequestration under a Mn-oxyhydroxide layer on the sediment surface. Reservoirs also enhanced diatom production and sedimentation of non-detrital Si, decreasing Si transport to the sea. Retention of total Fe, Si and P was 15%, 7% and 25% of the total river transport, respectively.The river-aquifer interface (hyporheic zone) functioned differently in the two rivers. Daily oscillating discharge in the regulated river and reduced spring peaks caused riverbed colmation, impairing river-aquifer exchange and forming stagnant subsurface areas. The hyporheic zone functioned as a source/sink of Fe, Mn, dissolved OC and NH4 in the regulated/unregulated river. Regulation also altered temporal hydraulic gradients dynamics between river and aquifer favouring solute pulses and presumably causing irregular TOC patterns at the river mouth.Hydrological modelling of river-aquifer interactions indicated that short-term regulation diminished orthogonal fluxes. Prolonged river flow peaks increased bank storage, favouring a release of nutrients and major/trace elements into the river during return flows. Colmation restricted water movement across the river-aquifer interface, increasing residence time and favouring suboxic conditions. Gently sloping river banks (former floodplains) of the regulated river facilitated river water entry to subsurface layers, potentially increasing solute export.Overall, modified river discharge altered river-aquifer spatial and temporal connectivity and interface biogeochemistry. Longitudinal connectivity was disrupted by long-term regulation, while lateral and vertical connectivity and hyporheic exchange were reduced by oscillating river water levels and clogging. These novel findings on post-regulation riverine hydrological pathways and geochemical fluxes can help sustain riverine ecosystems.Godkänd; 2014; 20140506 (dmysie); Dissertation defence 2014-09-12 Name: Dmytro Siergieiev Subject: Applied Geology Thesis: Hydrogeochemical effects of hydropower regulation on river-aquifer continuum in boreal rivers Examinator: Ass. Professor Angela Lundberg, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Opponent: Professor Hjalmar Laudon, Inst. för skogens ekologi och skötsel, Umeå Time: Fredag 12 September 2014 10.00 Place: E632, Luleå Unviversity of TechnologyGroundwater and Dependent Ecosystems: New Scientific and Technological Basis for Assessing Climate Change and Land-use Impacts on Groundwate

Aktivitet: Watershed Ecology and Biogeochemistry

Evenemang (konferens etc): Watershed Ecology and Biogeochemistry : 03/10/2013; Startdatum: 01/01/2013; Slutdatum: 01/01/2013; Roll: Deltagare; Typ: Organiserade av och deltagande i konferenser, workshops, kurser, seminarier - Deltagande i workshop, seminarium, kur

Aktivitet: Watershed Ecology and Biogeochemistry

Evenemang (konferens etc): Watershed Ecology and Biogeochemistry : 03/10/2013; Startdatum: 01/01/2013; Slutdatum: 01/01/2013; Roll: Deltagare; Typ: Organiserade av och deltagande i konferenser, workshops, kurser, seminarier - Deltagande i workshop, seminarium, kur

Simulation of nitrogen transformations in the mine water recipient at Boliden, Sweden, using system dynamics modeling

System dynamics modeling was performed in Brubäcken, the mine water recipient at Boliden, with the aim of predicting nitrogen transformations in the system. The 12-km-long Brubäcken system flows through Gillervattnet tailings impoundment and two lakes (Nya Sjön and Bruträsket), and finally discharges into the Skellefte River. Ammonium is the dominating nitrogen species in the system, and modeling focused on Nya Sjön, where NH4-N was present in concentrations up to 14 mg/l in 2006, and reached 6 mg/l in 2008. This concentration drop was related to the closing of the cyanide gold ore leach plant at Boliden in early 2008. Simulations of nitrogen transformations are based on a conceptual model that includes six nitrogen species involved in 16 different nitrogen transformation reactions occurring in the water column as well as in water- sediment and water-atmosphere interactions. Nitrogen species concentrations and process rates are simulated using the Powersim modeling software. Most of the reactions are considered to follow first-order kinetics Simulations showed high correlation between measured and predicted concentrations. The long-term stability of the model was tested in a six- year simulation using similar input data for all years. The stability of the model is judged to be satisfactory. A sensitivity analysis was also performed to identify the behavior of the model when input variables change ±10%. The results are presented graphically, and the most influential variables are identified. The model was finally validated using data from two years (2006–2007).Validerat; 20101217 (root

Hydrogeochemical assessment of surface water - groundwater interaction : model development

Godkänd; 2011; 20111016 (ysko

EFFECT OF TREATED WASTEWATER IRRIGATION ON VEGETABLES Vegetable Irrigation with

1 Treated waste water is normally used for irrigation purposes in countries sufferin

“Clogging layer” at regulated river beds - implications for river-groundwater exchange

Within the EU-project GENESIS (2013), aiming to provide scientific basis and technical guidance for the update of the EU Groundwater Directive, Luleå University of Technology is investigating possible effects of hydropower regulation on surface water (SW)- groundwater (GW) exchange. The study compares SW, GW and hyporheic processes for the unregulated Kalix River and the regulated Lule River. Hydropower has long been regarded a fairly green energy source but today negative effects have become obvious (Renöfält et al. 2010).The hyporheic zone (HZ) accommodates most of the SW-GW exchange of solutes just beneath and along a river, dampens heat fluxes, processes pollutants and is essential for ecosystems.The study observes SW and GW (in wells orthogonal to the river) at one site in each river. In these, hydrological (water level, hydraulic conductivity, tracer test) and geochemical (temperature, electrical conductivity, water/soil chemistry) measurements were performed during several seasons.The presence of natural high-flow events in the Kalix River removes fines from the river bed, maintaining good SW-GW connectivity that favours hyporheic exchange (Brunke and Gonser 1997). Altered discharge of the regulated river (reduced flow peaks and velocity, daily discharge fluctuations) facilitated deposition of fine sediments at the river bed forming a “clogging layer” (Blaschke et al. 2003). The bed in the regulated river has two orders of magnitude lower hydraulic conductivity than that at the unregulated site and restricts the SW-GW exchange.Reduced hydraulic connectivity between SW and GW at the regulated Lule River site suggests decreased fluxes across the river-aquifer interface (Siergieiev et al. 2013), and thus reduced size of the HZ which is not always the case in regulated rivers (Sawyer et al. 2009).Decreased hyporheic velocities led to increased residence time and favored prolonged contact between water and soil matrix that stimulated biogeochemical transformations. As a result, the electrical conductivity of hyporheic water of the Lule River was higher than that of the surrounding water.Deteriorated connectivity and extended travel time reduced the dissolved oxygen concentration, which is functionally ecologically essential for hyporheic habitat. In addition, complete consumption of nitrate found at the regulated site, suggests formation of a suboxic zone extending several meters inland which promotes metals release reflected in high dissolved Fe and Mn in the HZ. The conditions of SW-GW exchange control nutrients processing and their export to SW. Thus, the HZ in the Lule River acts as a source of dissolved metals, while in the Kalix River much of the metals are removed by hyporheic processes due to good SW-GW connectivity.SW-GW connectivity plays an important role for hyporheic exchange and hyporheic water quality. Hydropower regulation in the Lule River has altered this connectivity, which may have far reaching implications for biogeochemical processes in the river.Godkänd; 2013; 20131024 (dmysie