Hydrological Observatory description

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RIVER PÄRNU, ESTONIA Location The Pärnu river catchment area is situated in Western Estonia and drains 6,900 km² to the Bay of Pärnu, which is northern part of the Gulf of Riga.

Catchment description The Pärnu River catchment is predominantly agricultural; the main pollution point-sources are the cities of Pärnu, Paide and Türi.

Non-treated wastewater and stormwater is discharged into Pärnu River at Siimu bridge, Rääma Brook and Tähe.

1 RIVER PÄRNU, ESTONIA Location The Pärnu river catchment area is situated in Western Estonia and drains 6,900 km² to the Bay of Pärnu, which is northern part of the Gulf of Riga. It is one of the longest rivers in Estonia: 144 km long. Catchment description The Pärnu River catchment is predominantly agricultural; the main pollution point-sources are the cities of Pärnu, Paide and Türi. About 85% of wastewater and stormwater of Pärnu Town is discharged from the waste water treatment plant via the deep-sea outlet into the Gulf of Pärnu. Non-treated wastewater and stormwater is discharged into Pärnu River at Siimu bridge, Rääma Brook and Tähe. Pärnu River basin is located at the outcrop area of Lower Silurian and Middle Devonian deposits. Northwards from Pärnu River Navesti River line is the outcrop area of Lower Silurian limestone and dolomite, southwards those are covered by Middle Devonian sandstone, aleurolites and clay. Topsoil thickness at the northern and eastern part of the river basin is mostly less than 5 meters (less than 1 meter at some areas), but at the southern part the topsoil thickness is up to 60 meters. Sandy loam moraine is mainly spreading at areas with smaller thickness of topsoil. At the lower course of Pärnu River moraine is covered by thick (up to meters) varved clay layer, covered by marine genesis sands. Key descriptors Catchment area 6920 km 2 Mean altitude above the Sea level 50 m Maximum Altitude 78 m Mean flow 64,4 m 3 /s 97% exceedance(q97) 26,8 m 3 /s Long-term annual precipitation 700 mm (Pärnu MS)

D2 ar sandstone, silt, clay, dolomite-rich marl, dolostone D2 br sandstone, silt, clay D2 nr dolomite-rich marl, dolostone, clay, silt, sandstone D2 pr sandstone, silt, clay, dolostone, dolomite-rich

2 D2 ar sandstone, silt, clay, dolomite-rich marl, dolostone D2 br sandstone, silt, clay D2 nr dolomite-rich marl, dolostone, clay, silt, sandstone D2 pr sandstone, silt, clay, dolostone, dolomite-rich marl S1 ad marl, limestone S1 jg limestone, marl, dolostone S1 jn marl, clay-rich limestone, dolostone S1 jr limestone, marl S1 rk limestone, dolostone Hydrological summary Variations of runoff are big, since there are few lakes at the river basin territory. Pärnu River runoff is highest in April and lowest in July according to the results of long-term observations. Spring flood peak at the upper course of Pärnu River is on average 20 days later than at the lower course. Difference of runoff minimum and maximum at Pärnu River Oore hydrological station is over a hundred times. The small slope enhances extensive floods and swamping of the lands, 22% of the river basin territory are wetlands. Flat relief and low runoff also enhance overgrowing of the river during the low flow period.

3 Figure. Long-term streamflow (m 3 /s) for the Oore hydrological monitoring station: annual (series1), spring max (series2), winter min (series3) and summer min (series4). Data availability Flow data are measured at the 9 hydrological stations and water quality parameters at 5 monitoring stations. Daily flow and supplementary hydrological information is available from the Estonian Meteorological and Hydrological Institute from Measured data and equipment descriptions, and frequency of measurement can be downloaded from the EMHI home page ( The regular water quality information is available from 1992 from the Tallinn University of Technology, and irregular information (four times a year) - from 1960 s. Bigger tributaries and their hydrological parameters at the downstream cross-section are shown in the table below. River Station Period of observations area, Q, m 3 /s km 2 long-term M, l*s/km 2 long-term Qmax,1% (m 3 /s) Q min (95%) summer Pärnu Tahkuse ,8 8, ,7 1,9 Pärnu Oore , ,6 4,95 Navesti Aesoo ,1 9, ,6 0,6 Halliste Riisa ,7 9, ,2 1,4 Q min (95%) winter

4 Supporting data are also available: maps of hydro-geological, soil-types, topography etc.

5 Research Activity and Outputs River Pärnu catchment area is covered by different research projects and their outputs are available in digital and hard copy format. River water quality model QUAL2K and the Wennerblom (Älvsborg) diffused pollution model were simultaneously applied for water quality and land-based pollution estimations. The Pärnu River basin was chosen for testing the tool (Ennet et al, 2008). Institutional Support All environmental monitoring stations are operated under the state supervision according the National Environmental monitoring programme. Value to network The River Pärnu is located in a region of high agricultural and urban activity. Human impact on the water quality and resources are considerable. Impact of climate change on water resources in Estonia is under the investigation, but preliminary results indicate that hydrological changes are found mostly in early spring and winter time, when the spring floods are becoming lower and winter low flow higher. This influences the agricultural practices and water quality in general. The Pärnu Observatory provides data for hydrological conditions that are common in its region but which are quite different from those monitored by many other observatories in the network. Some distinguishing features of the Pärnu catchment in the European context are: high precipitation, high flow variability, high human impact on water quality, widespread wetlands and frequent inundation due to flat terrain. Contact information: Alvina Reihan, Department of Environmental Engineering, Tallinn University of Technology, Alvina.reihan@ttu.ee References 1) Ennet. P., Pachel, K., Viies, V., Jürimägi, L. and Elken, R.2009.Estimating water quality in river basins using linked models and databases. Estonian Journal of Ecology, 2008, 57, 2, ) Iital, A., Loigu, E. & Vagstad, N Nutrient losses and N & P balances in small agricultural watersheds in Estonia. Nord. Hydrol., 34, ) Iital, A., Stålnacke, P., Deelstra, J., Loigu, E. & Pihlak, M Effects of large-scale changes in emissions on nutrient concentrations in Estonian rivers in the Lake Peipsi drainage basin. J. Hydrol., 304(1.4),

6 4) Türk, K., Leetsar, J., Pachel, H., Truu, K. & Sild, H Eesti NSV jõgede arvutuslik veekvaliteet. Eesti Maaparandusprojekt, Tallinn. 5) Uuemaa, E., Roosaare, J. & Mander, Ü Landscape metrics as indicators of river water quality at catchment scale. Nord. Hydrol., 38(2), ) Vassiljev, A Comparison of two one-dimensional nitrogen leaching models at the watershed scale. Envir. Eng. Sci., 23(1), ) Wade, A. J., Neal, C., Whitehead, P. G. & Flynn, N. J Modelling nitrogen fluxes from the land to the coastal zone in European systems: a perspective from the INCA project. J. Hydrol., 304, ) Wulff, F., Bonsdorff, E., Gren, I.-M., Johansson, S. & Stigebrandt, A Giving advice on cost effective measures for a cleaner Baltic Sea: a challenge to science. Ambio, 30(4.5), ) Lääne-Eesti vesikonna Pärnu alamvesikonna veemajnduskava. Water management programme of Pärnu river basin Eesti Keskkonnaministeerium, Tallinn Some more information is available from the Pärnu river basin water management plan projekt.pdf

NITRATE MONITORING RESULTS IN AGRICULTURAL CATCHMENTS

Environmental Engineering NITRATE MONITORING RESULTS IN AGRICULTURAL CATCHMENTS Latvia University of Agriculture e-mail: ainis.lagzdins@llu.lv Abstract The paper deals with monitoring results of nitrate