Browsing by Subject "runoff"

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  • Johansson, Frank; Heino, Jani; Coiffard, Paul; Svanbäck, Richard; Wester, Jacob; Bini, Luis Mauricio (Springer Nature, 2020)
    Scientific Reports
    Citizen science data (CSD) have the potential to be a powerful scientific approach to assess, monitor and predict biodiversity. Here, we ask whether CSD could be used to predict biodiversity of recently constructed man-made habitats. Biodiversity data on adult dragonfly abundance from all kinds of aquatic habitats collected by citizen scientists (volunteers) were retrieved from the Swedish Species Observation System and were compared with dragonfly abundance in man-made stormwater ponds. The abundance data of dragonflies in the stormwater ponds were collected with a scientific, standardized design. Our results showed that the citizen science datasets differed significantly from datasets collected scientifically in stormwater ponds. Hence, we could not predict biodiversity in stormwater ponds from the data collected by citizen scientists. Using CSD from past versus recent years or from small versus large areas surrounding the stormwater ponds did not change the outcome of our tests. However, we found that biodiversity patterns obtained with CSD were similar to those from stormwater ponds when we restricted our analyses to rare species. We also found a higher beta diversity for the CSD compared to the stormwater dataset. Our results suggest that if CSD are to be used for estimating or predicting biodiversity, we need to develop methods that take into account or correct for the under-reporting of common species in CSD.
  • Spilling, Kristian; Asmala, Eero; Haavisto, Noora; Haraguchi, Lumi; Kraft, Kaisa; Lehto, Anne-Mari; Lewandowska, Aleksandra; Norkko, Joanna; Piiparinen, Jonna; Seppälä, Jukka; Vanharanta, Mari; Vehmaa, Anu; Ylöstalo, Pasi; Tamminen, Timo (Elsevier BV, 2022)
    Data in Brief
    Climate change is projected to cause brownification of some coastal seas due to increased runoff of terrestrially derived organic matter. We carried out a mesocosm experiment over 15 days to test the effect of this on the planktonic ecosystem. The experiment was set up in 2.2 m3 plastic bags moored outside the Tvärminne Zoological Station at the SW coast of Finland. We used four treatments, each with three replicates: control (Contr) without any manipulation; addition of a commercially available organic carbon additive called HuminFeed (Hum; 2 mg L−1); addition of inorganic nutrients (Nutr; 5.7 µM NH4 and 0.65µM PO4); and a final treatment of combined Nutr and Hum (Nutr+Hum) additions. Water samples were taken daily, and measured variables included water transparency, organic and inorganic nutrient pools, chlorophyll a (Chla), primary and bacterial production and particle counts by flow cytometry.
  • Gyawali, Arun (Helsingin yliopisto, 2018)
    The balance between incoming precipitation (rainfall and snowfall) and outgoing evapotranspiration (ET), runoff and drainage to and from an ecosystem plus changes in soil moisture storage and the water equivalent of the snowpack is known as the water balance. A dominating feature of the water balance in the boreal zone is snowpack accumulation over winter and the spring snowmelt, both of which are affected by forest. In Finland, there are strong north-south gradients in the amount of precipitation, the proportion of rainfall and snowfall and temperature, and therefore latitudinal differences in the water balances components can be expected. Furthermore, the large canopy and deeper rooting of trees, together with the presence of a permanent ground vegetation cover, result in significant differences in interception, infiltration and water balance outputs of forests compared to other forms of land-use. Because of morphological and ecophysiological differences between the trees species, the water balance of Norway spruce and Scots pine dominated forests can be expected to differ. Determining the water balance of forest ecosystems across Finland would, therefore, help in assessing the hydrological ecosystem services provided by forests and form a basis for examining the effects of climate change and forest management on the water balance. This study aimed to compute the daily water balance of six Norway spruce, and three Scots pine dominated mature forest stands (plots) located throughout Finland over a 26-year study period (1990-2015). It was hypothesized that the various water balance components would systematically vary with latitude, a surrogate for climate, and differ between spruce and pine stands. The daily version of the water balance model “WATBAL” developed by Mike Starr (University of Helsinki, Dept. Forest sciences) was used for this study. The model requires daily meteorological data (precipitation, temperature, global radiation), stand parameters (canopy cover, rooting, crop coefficient), soil parameters (including infiltration coefficient, soil moisture contents at permanent wilting point, field capacity and saturation, and two soil moisture parameters for a plant available water content function). Six of the plots had soil developed in till and 3 plots had soil developed in sorted glaciofluvial deposits. Plot meteorological data for 1990-2015 was derived using spatially interpolated gridded data. If the daily air temperature was ≤0°C, any precipitation was assumed to be snowfall. The stand and soil parameters were derived from data collected from the 9 study plots by Luke (formerly Metla). The nine plots belong to the Finnish network of ICP-Forest level II plots that have been established throughout Europe. Pedotransfer functions (PTF) based on soil texture and organic matter contents were used to derive initial values for the soil hydraulic parameters. Time domain reflectometry (TDR) measured soil moisture data was available for 7 of the plots and, after carrying out careful quality control and rejection of outliers, used for calibration of modelled soil moisture and optimization of soil hydraulic parameters for those plots. Optimization was carried out using the non-linear Marquardt regression method. Goodness-of-fit for soil moisture was evaluated using correlation and R2 values from linear regression. After computing the daily water balance with the WATBAL model (using optimized soil hydraulic parameter values for the 7 plots and initial PTF values for the remaining 2 plots) the long-term mean annual and mean daily water balance components (with a 7-day moving average smoothing) were calculated. The water balances were computed for the humus layer plus 0-40 cm soil layer, which, based on literature, would have included most if not all of the roots. The dependence of the mean annual water balance components on latitude was evaluated using correlation analysis and linear regression, and the effect of tree species was tested for using the t-test on pairs of spruce-pine plots located close to each other. The raw TDR data was found to contain a considerable amount of gaps and erroneous (too high) values, often associated with the spring snowmelt. Optimization of the soil hydraulic parameters using the measured soil moisture contents calculated from the “cleaned” TDR data for the snow-free period resulted in a highly significant (p<0.001) Pearson correlation of +0.85 (R2 = 0.75) for the fit between measured and modelled soil moisture contents calculated across all 7 plots. The correlations for the individual plots were also highly significant. Based on the optimized WATBAL output, the fraction of plot mean annual precipitation as snowfall ranged from 20 to 29%. Corresponding ranges for ET, drainage and runoff were respectively 33 to 57%, 24 to 42%, and 18 to 25%. The mean annual water balance components were found to be significantly correlated to latitude, reflecting trends in precipitation and temperature. Evapotranspiration decreased with increasing latitude while maximum snow-on-ground, snowmelt and associated runoff increased with increasing latitude. Spruce mean annual ET was 9% higher than pine in one of the paired plot sets and 37% higher in the other set. For drainage, pine was 15% greater than spruce in one of the paired plot set and 74% higher in the other set of paired plots. There were no significant differences between spruce and pine plots for snowmelt and runoff. Variation around these trends were related to differences in soil hydraulic properties among the plots which, in turn, were related to differences in parent material and soil texture. The overall conclusion from this study was that the daily water balance of the forested plots could be realistically modelled using such a relatively simple water balance model as WATBAL. The importance of spatially representative and accurate soil moisture measurements for model calibration purposes was highlighted. While the importance of snowfall on the water balance increased northwards regardless of tree species, evapotranspiration was determined by both latitude and by species. Climate change can therefore be expected to have a significant impact on the water balance of Finnish forests resulting in environmentally important changes in leaching and runoff.
  • Päivänen, Juhani (Suomen metsätieteellinen seura, 1974)
  • Stuart, Elliot (Helsingfors universitet, 2013)
    The primary characteristic of urbanisation is the addition of hard surfaces to catchments, which affects water and habitat quality in urban streams and alters natural hydrological processes by reducing infiltration, evapotranpiration and efficiently conveying storm runoff to streams, gathering a variety of urban polluants along the way. This is typical of the 'urban stream syndrome'. Catchment imperviousness (especially Effective Impervious Area or percent connectivity) can be used as one of the primary indicators of the severity of this phenomenon. This research was initiated through a collaboration between the City of Helsinki and the University of Helsinki to determine the baseline water quality of Hakuninmaanoja, a small urban stream in Helsinki, Finland, and the imperviousness of its catchment, where a pilot ecological housing development 'Kuninkaantammi' (KUNTA) will be built beginning in 2013. The purpose of the project is to assess the current characteristics of the catchment prior to the development in the headwaters of the stream. An automatic water quality monitoring station was built on the lower part of the stream approximately 200m upstream of its junction with Mätäjoki, the second largest river of Helsinki. Water Sensitive Urban Design can be used as part of a holistic stormwater treatment train to limit newly created imperviousness, and minimise the connectivity of the necessary remainder, allowing stormwater runoff to be reused, infiltrated and treated through soil media, or slowed down enough to attenuate the urban hydrograph. Some of these features such as raingardens, green roofs and detention ponds will be included in the KUNTA development for this purpose. A detailed calculation of catchment imperviousness was completed via field survey and land use categorization methods. Total Impervious Area (TIA) was determined to be 22%, Effective Impervious Area 15% and catchment wide runoff coefficient given by land use categorisation method to be 0.32. TIA is expected to increase to 30% following development of KUNTA, however EIA is not expected to increase in proportion with TIA due to planned Water Sensitive Urban Design features. Yearly runoff volumes based on each method of calculating imperviousness were estimated, as well as for the future following KUNTA development. Water quality in the stream currently is quite satisfactory in relation to other streams in Helsinki, however the urban stream syndrome is already evident with particular concern regarding temperature, sediment and peak flow fluctuations. Effective Impervious Area should be used in urban planning of new and existing developments rather than TIA because it will give much greater accuracy of runoff volumes and infiltration rates by taking into account unconnected impervious surfaces. Strengthening local solutions to reduce connectivity should be a municipal priority. Water quality monitoring will continue at the site until after KUNTA has been built, and further research should focus on determining the technical performance of stormwater Best Management Practices (BMPs) at the site.