Continental Scale Modelling of Water Quality in Rivers

Global and continental scale modelling has been confined to water quantity (e.g. WaterGAP - Water Global Assessment and Prognosis (Alcamo et al. 2003), GWAVA - Global Water AVailability Assessment (Meigh et al, 1999)). Here we describe an approach to include water quality at these scales within the WaterGAP model. The application is to the pan-European area and is being carried out within the EU-funded SCENES Project which has the principal goal of developing new scenarios of the future of freshwater resources in Europe. The model operates on 5x5 arc-minute grid squares. Water flows in and between grid cells are provided by WaterGAP. The water quality loadings into the river system comprise point sources (domestic effluent, manufacturing discharges and urban runoff) and diffuse sources (runoff from land and scattered settlements not connected to the public sewerage system). Point source loadings are calculated for each country using easily available datasets. For example, the domestic load is a per capita emission factor times by country population multiplied by the percentage of the population connected to the sewage system, which is then reduced by the amount removed in each of three types of sewage treatment (primary, secondary and tertiary). Data on the amount treated in different types of sewage works is set for each country, while the amount removed by treatment types will vary with the water quality variable being modelled. Country level data is converted to grid square data required by the model, according to the population in each grid square. Diffuse sources from land are calculated by regression models based on runoff and land use (e.g. numbers of livestock) for each model grid square. The modelling system has currently been set up to simulate biochemical oxygen demand (BOD) and total dissolved solids. The model was tested against measured longitudinal profiles and time series data for BOD on contrasting rivers e.g. the River Thames (UK) driven by domestic loading and the River Ebro (Spain) with a high share of discharges from livestock farming. Further developments will see the inclusion of total nitrogen (TN), total phosphorus (TP) and dissolved oxygen. Within the SCENES project a set of future scenarios reflecting different outlooks on Europe has been developed, called “Economy First”, “Fortress Europe”, “Sustainability Eventually” and “Policy Rules”. An Expert Panel was used to suggest what these futures would mean for drivers of water quantity and water quality across pan-Europe. We have projected how changes in percentage population connected to sewers, the level of sewage treatment and population would change loadings from domestic effluent for TN, TP and BOD. In time, these will be used to predict future water quality in European rivers

Alternative approaches to modelling lake ecosystems

The development of modelling in aquatic ecology has focused on mechanistic biogeochemical models.  However, such models have substantial data requirements for inputs and also for proper validation, which hinders their use for less studied systems.  Another significant problem with complex models is their structural and computational difficulty, and thus often an associated absence of proper uncertainty analysis for the model results.  This makes the use of the outputs for public policy making (e.g. in lake management) rather questionable.  We see no compelling reason (other than lack of awareness of choices) why all lakes and all questions should necessarily be studied using the same high-profile models.  Here we review two alternative statistical approaches, Linear Mixed Modelling and Structural Equation Modelling, and the different ways they have been used to extract maximum information from existing data.  These methods offer promise for tackling the problems highlighted above, although our aim is not to promote any one method over the others.  Rather, we want to stimulate debate about the remaining unknown factors in lake modelling as well as about the balance between data and models, and the still too uncritical way in which model outputs are interpreted and used for decision making

Causal analysis of phytoplankton development in a small humic lake using structural equation modelling

The factors affecting phytoplankton development in a small boreal, dystrophic lake during summer stratification were explored using structural equation models (SEM). Phosphorus had the highest positive impact on phytoplankton, and higher temperatures also enhanced the biomass. Water colour, and to a lesser extent intense zooplankton grazing, restricted phytoplankton biomass. Grazers generally seemed to be ineffective at controlling phytoplankton, however, which could be partly due to the high abundance of Gonyostomum semen (Raphidophyceae), a large motile algae not readily grazed by zooplankton. The importance of water colour, a significant factor in dystrophic lakes, emerged clearer in SEM than from regression models. SEM proved to be an effective and informative technique for exploring the factors affecting phytoplankton development, the role of each variable, and their interactions. Incorporating Bayesian analysis into the traditional SEM enabled a more detailed examination of variation in the variable estimates and possible sources of uncertainty and provided more reliable error estimates. We used total chlorophyll a as a proxy for total phytoplankton biomass, but the results clearly indicated that some of the emerging questions could have been better addressed by separating different phytoplankton groups. Nevertheless, SEM provided new insights from standard data, and we encourage its further applications in aquatic science

Participatory operations model for cost-efficient monitoring and modeling of river basins — A systematic approach

AbstractThe worldwide economic downturn and the climate change in the beginning of 21st century have stressed the need for cost efficient and systematic operations model for the monitoring and management of surface waters. However, these processes are still all too fragmented and incapable to respond these challenges. For example in Finland, the estimation of the costs and benefits of planned management measures is insufficient. On this account, we present a new operations model to streamline these processes and to ensure the lucid decision making and the coherent implementation which facilitate the participation of public and all the involved stakeholders. The model was demonstrated in the real world management of a lake. The benefits, pitfalls and development needs were identified. After the demonstration, the operations model was put into operation and has been actively used in several other management projects throughout Finland

Datafuusiomenetelmän käyttö kalankasvattamoiden vedenlaatuvaikutusten seurannassa Saaristomerellä

Kalankasvatuksen kestävän kehittämisen kannalta on olennaista tietää, kuinka paljon kalankasvattamo tai muu toiminta kuormittaa ympäristöä ja vaikuttaa vesien ekologiseen tilaan. Tässä työssä Saaristomeren kasvattamoiden vaikutuksia veden a-klorofylli-pitoisuuteen tarkasteltiin velvoitetarkkailuun liittyvän näytteenoton, SYKEn satelliittikuvatulkintojen sekä vuonna 2019 toteutettujen intensiivimittausten avulla. Eri menetelmillä tuotettu mittaustieto yhdistettiin SYKEn datafuusio-järjestelmällä. Yhdistämisen tuloksena saatiin vuoden 2019 ja 2020 kasvukauden päivittäiset a-klorofylli-pitoisuuden karttakuvat ja aikasarjat laitosten ympäristöistä ja koko Saaristomeren alueelta. Neljän kasvattamon vaikutuksia tarkasteltiin tarkemmin. Niillä ei ollut datafuusio-menetelmän tarkkuuden rajoissa havaittavia vaikutuksia a-klorofyllin pitoisuuteen. Erilaisten mittausten yhdistäminen paransi vaikutusarvioiden alueellista ja ajallista kattavuutta ja luotettavuutta. Jotta mahdolliset vähäiset vaikutukset saadaan havaittua avomerelläkin, datafuusiota tulee edelleen kehittää ja yhdistää virtaus-vedenlaatumalleihin. Merkittäviä parannuksia voidaan saada myös anturimittausten ja satelliittitulkintojen tarkkuutta parantamalla