DWARF

Drinking WAter Readiness for the Future

The Drinking WAter Readiness for the Future project benefits from a € 1 mil. grant from Norway and Technology Agency of the Czech Republic.

Increasing levels of Dissolved Organic Matter (DOM) is a large challenge for Drinking Water Treatment Plants. Surface water is the source for more than 50% of drinking water in the Czech Republic. In the region of South Bohemia surface water supports drinking water for more than 350 thousand people from the reservoirs and Otava River. Catchments of these sources will be characterized with respect to the sources of DOM and their temporal and spatial variability resulting in a map of DOM sources with future predictions. A methodology for outflow control in reservoirs to minimize the effect of flood events with high DOM levels will be developed. A cooperation among basin authorities, drinking water producers and Czech and Norway research partners will be established.

Project

Concentrations of dissolved organic matter (DOM) are increasing in surface waters and the water is becoming more coloured (browning). This poses large challenges for drinking water treatment plants (DWTP) using surface water as raw water sources. This project is building on insights gained from a previous Nordic project (NOMiNOR) on browning of waters and its impact on water treatment. The project proposal applies those insights to a case study in the Czech Republic and at the same time contextualises and enhances our knowledge on the topic.

Thus, the two main objectives of the DWARF project are to:
1) Strengthen the conceptual understanding of the link between governing factors on the amount and characteristics of DOM in raw water sources for drinking water plants, and
2) Increase levels of knowledge and competence on DOM treatability, optimum DOM removal in water treatment and DOM control during water treatment and distribution.

To achieve these objectives, we need to unravel the concurrent governing factors for temporal and spatial differences between the amount and physicochemical characteristics of the raw water. This will be achieved through multivariate statistical analysis comparing climate and catchment information with data of water chemistry and DOM characteristics from monitoring and comprehensive characterization of raw and treated water samples. Main catchment characteristics are vegetation, land use, geology and soil type/morphology. Raw water samples from surface waters used for preparation of drinking water will be collected during winter, spring, summer and autumn periods, as well as during episodes of different flow regimes.

Published results

Relationships between a catchment-scale forest disturbance index, time delays, and chemical properties of surface water. Susanne I. Schmidt, Josef Hejzlar, Jiří Kopáček, Ma. Cristina Paule-Mercado, Petr Porcal, Yuliya Vystavna, Ecological Indicators 125 (2021), 107558

Forest disturbances influence water quantities and qualities in catchments, but these disturbances cannot be easily measured and quantified directly. The two main options are direct tree counting and the use of satellite images, from which forest disturbance indices are calculated. The problem with the first option is that it is time consuming. To overcome this problem, we used a catchment-scale infrared (IR) index for a Picea abies mountain forest catchment, validated by tree counting, as a predictor in regression modeling to assess the water chemical property response to disturbances. This enabled us to quantify the time delay with which chemical compounds in surface waters reacted to disturbances. The results showed that there was an insignificant correlation between dissolved organic carbon (DOC) concentration and the disturbance index from the same year that the disturbance occurred (R2 = 0.02; p = 0.27), but correlations gradually improved and became more significant, with correlations after a 6-year delay being strongest (R2 = 0.69; p ≤ 0.001). The significant time delays with which other compounds responded to the disturbance ranged from 0 years (NO3-N, total nitrogen, Ca2+, Mg2+, labile aluminium) to 5 years (total organic nitrogen). Our results suggest the potential use of such an index for predicting water quality changes in disturbed areas of Picea abies mountain forests.

Forest damage and subsequent recovery alter the water composition in mountain lake catchments

Forest damage by insect infestation directly affects the trees themselves, but also indirectly affects water quality via soil processes. The changes in water composition may undergo different pathways depending on site-specific characteristics and forest components, especially the proportion of coniferous and deciduous trees. Here, we test whether changes in forest components and the intensity of disturbance can predict the chemical properties of water outflow from affected lake catchments. Information about forest regeneration (a phase dominated by deciduous trees) and the proportions of damaged and healthy coniferous trees and treeless areas were obtained from satellite data. The four study catchments of Prášilské, Laka, Plešné, and Čertovo lakes are geographically close and located in the same mountain range (Šumava Mts., Czech Republic) at similar altitude, but they differ in extents of forest disturbances and recoveries. The water quality measured at the lake catchment outflows differed, and better reflected the development of forest components and health than did meteorological (temperature and precipitation) or hydrological (discharge) variables. Several of the outflow properties (concentrations of inorganic aluminium, protons, potassium, calcium, magnesium, alkalinity, dissolved organic carbon (DOC), nitrate, and total phosphorus), responded catchment-specifically and with different delays to forest disturbance. The most pronounced differences occurred in DOC concentrations, which started to increase in the most disturbed Plešné and Laka catchments 7 and 6 years, respectively, after the peak in tree dieback, but did not increase significantly in the Prášilské catchment, which was disturbed several times during the last 3–4 decades. This study demonstrates an importance of extents of forest disturbances, the following changes in forest composition, and catchment-specific characteristics on water composition.

Nutrient dynamics in temperate European catchments of different land use under changing climate

Our study underlines that current climate change and associated hydrological changes, such as decrease in flow, play an important role in the transport and dynamics of nutrients in the catchment. We have found that due to the different origins and pathways, individual nutrients had diverse behaviour patterns in streams and responded differently to changing climate. Hydrological patterns in streams became clear when systematic and continuous monitoring under a changing climate was applied, highlighting the need for such data to better understand the impact of hydrological drivers, particularly for long-term dynamics. In three studied catchments, streamflow showed a decreasing trend in line with rising air temperature, declining snow cover and increasing evapotranspiration. Time series analyses of nitrate concentrations revealed decreasing trends, whereas dissolved organic carbon increased in all catchments regardless of land use. Long-term trends of total phosphorus concentrations were positive in anthropogenically impacted streams. Stable nitrate isotopes indicated distinct nitrate sources and processes, but also their seasonality in relation to hydrological patterns and land use.

Distinguishing between Sources of Natural Dissolved Organic Matter (DOM) Based on Its Characteristics

Increasing levels of dissolved organic matter (DOM) in watercourses in the northern hemisphere are mainly due to reduced acid rain, climate change, and changes in agricultural practices. However, their impacts vary in time and space. To predict how DOM responds to changes in environmental pressures, we need to differentiate between allochthonous and autochthonous sources as well as identify anthropogenic DOM. In this study we distinguish between allochthonous, autochthonous, and anthropogenic sources of DOM in a diverse watercourse network by assessing effects of land cover on water quality and using DOM characterization tools. The main sources of DOM at the studied site are forests discharging allochthonous humic DOM, autochthonous fulvic DOM, and runoff from urban sites and fish farms with high levels of anthropogenic DOM rich in protein-like material. Specific UV absorbency (sUVa) distinguishes allochthonous DOM from autochthonous and anthropogenic DOM. Anthropogenic DOM differs from autochthonous fulvic DOM by containing elevated levels of protein-like material. DOM from fishponds is distinguished from autochthonous and sewage DOM by having high sUVa. DOM characteristics are thus valuable tools for deconvoluting the various sources of DOM, enabling water resource managers to identify anthropogenic sources of DOM and predict future trends in DOM.

The technological development of drinking water treatment plants in the Czech Republic

Several actors have an impact on the quality of drinking water, but ultimately drinking water treatment plants (DWTPs) play a decisive role in ensuring that water quality complies with public regulations. Several developing technologies are combined in water treatment processes. In this paper, we are analysing the technological development of DWTPs in the South Bohemian region of the Czech Republic. The empirical basis is five DWTPs of varying size, and data are gathered through semi-structured interviews with relevant staff inside and outside of the five DWTPs. This study identifies the interplay of factors driving technological development: public regulations, the economic capacity of local DWTP owners together with subsidies from the European Union and national authorities, political priorities by local authorities, and the knowledge network. The paper addresses learning–knowledge–change processes of DWTPs, thereby contributing to our understanding of developing competence in producing drinking water. Generally, large DWTPs are front-runners in introducing new technologies while the smaller ones are lagging. Still, private companies operating small plants on behalf of municipal owners ensure that those DWTPs are part of a wider knowledge network, aiding to introduce a necessary and cost-effective upgrade to treatment steps.

Predicting the dissolved natural organic matter (DNOM) concentration and the specific ultraviolet absorption (sUVa) index in a browning central European stream

Over the past four decades, an increase in Dissolved Natural Organic Matter (DNOM) and colour, commonly referred to as browning, has been noted in numerous watercourses in the northern hemisphere. Understanding the fluctuations in DNOM quality is a prerequisite for gaining insights into the biogeochemical processes governing DNOM fluxes. Such knowledge is also pivotal for water treatment plants to effectively tailor their strategies for removing DNOM from raw water. The specific ultraviolet absorbance (sUVa) index has been a widely applied measurement for assessing DNOM quality. The sUVa index is the UV absorbance (OD254) of water normalized for DNOM concentration. We have used a long-term dataset spanning from 2007 to 2022, taken from the Malše River in South Bohemia, to model DNOM and the sUVa index. We have applied regression models with a processoriented perspective and have also considered the influence of climate change. Both DNOM and the sUVa index is positively related to temperature, runoff and pH, and negatively related to ionic strength over the studied period. Two distinct model approaches were employed, both explaining about 40% of the variation in sUVa over the studied period. Based on a moderate IPCC monthly climate scenario, simulations indicate that both DNOM and the sUVa index averages remain fairly stable, with a slight increase in winter season minima projected towards the year 2099. A slight decline in summer season maxima is simulated for DNOM, while the sUVa summer maximum remain stable. These findings suggest a robust resilience in both DNOM and the sUVa index against anticipated changes in temperature and runoff for the Malše River in South Bohemia.