Land-use management the crucial force driving the water quality in the catchment

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1 Land-use management the crucial force driving the water quality in the catchment Výzkumný ústav meliorací a ochrany půdy, v.v.i, Praha Antonín Zajíček, Petr Fučík, Tomáš Kvítek, Zbyněk Kulhavý, Pavel Novák (zajicek.antonin@vumop.cz)

2 The area of interest: Švihov potable water reservoir basin Built in 1972 Flooded area ha Lenght 39.1 km Total water volume mil. m³ Watershed km² Max. water uptake: 7.7 m 3 /s Serves for ca 1.5 mil inhabitants

3 Potable Water Reservoir Švihov Mainly agricultural watershed Lots of tributaries have worsened water quality Main problem - nitrates

4 Water quality and its trends in Jankovský potok catchment one of tributaries The area: ha Jankovský potok catchment The elevation: m a.s.l

5 Analyse of water quality and its trends in the Jankovský potok catchment Two sites are discussed here: Closting profile n th. order catchment 9617 on Hejnický stream the rightsite tributary Measuring sites Sterams Water reservoir Catchment of 4th. order

6 Jankovský potok- site 5600: N-NH 4 : C90 = 0.18 mg/l = I. quality class, insignificant fall N-NO 3 : C90 = 7.9 mg/l = IV. quality class, insignificand fall N-NO 2 : C90 = mg/l IV. quality class, insignificant fall P-PO 4 : C90 = 0,082 mg/l significant fall in concentrations, but higher than mg/l eutrophication limit! P-Tot: C90 = mg/l = III. quality class significant fall in concentrations higher than 0.1 mg/l limit!

7 Jankovský potok- site 5600

8 Hejnický potok site 9617: trends N-NH4 : C90 = 0.13 mg/l = I. quality class, without trend N-NO 3 : C90 = 6.8 mg/l = III. quality class, insignificand fall N-NO 2 : C90 = mg/l = IV.quality class, without trend P-PO 4 : C90 = mg/l significant fall in concentrations P-Tot: C90 = mg/l = III. quality class significant fall in concentrations but still higher than 0.1 mg/l limit!

9 Hejnický potok- site 9617

10 The effect of land-use on nitrate leaching

11 The effect of land-use on nitrate leaching

12 The effect of land-use on nitrate leaching Recently well-known and acceped principle Nitrate concentrations rise in the direction: forest meadows pastures arable land The nitrate concentrations variability is strongly correlated with land use (R 2 = 0.89) The NO 3- concentrations in the Czech Republic are not correlated with the amount of nitrogen fertilizers Nitrogen leaching is supposed to be proportional to the portion of arable land in the catchment Ploughing changes physical and chemical propertios of the soils (aeration, mineralisation, fall in denitrification rate)

13 The effect of tile drainage on nitrate leaching: Drainage systems are of the most important factors for N leaching. The portion differes according the reginonal charcteristics: Germany ca. 50% USA (Iowa) 80-90% CZ ca. 20% - but few data Three main effects: Doležal (2003) 1st. effect (temporary) rapid mineralisation of accumulated org. material followed by NO 3 leaching after building drainage system 2nd. effect (permanent) - the change of runoff pathways (vyšší proplavení půdy, hastened runoff, drying of shallow aquifers). 3th. effect (permanent) drained area in not suitable for denitrification (aeration)

14 Changes of nitrate concentrations in surface waters influenced by land use in the crystalline complex of the Czech Republic

15 Landuse in monitored districts: Český Krumlov district: grasslands established at many submontane sites where use as pastures is more suitable from a soil protection and water management perspective than ploughing. Between 1990 and 2000, area of permanent grassland in Cesky Krumlov district increased from km2 to km2, approximately 55% The Pelhřimov district landuse almost without change

16 Upper Vltava Ž E L I V K A

17 Evaluated: 8 catchments in Upper Vltava basin 23 catchments in Želivka basin Monitored periods Pelhřimov district : Český Krumlov district: a Trend analysis of nitrate concentrations Švihov basin: 10 catchments slightly increase 13 catchments slighltly decrease Upper Vltava basin: 8 catchments strong and significant decrease

18 Relationship between ploughed land and nitrate concentrations Vliv zornění na koncentraci dusičnanů v povodích vodárenských nádrží v povodí Vltavy R 2 = 0,7516 The effect of arable land share on nitrate concentrations in Vltava river reservoirs C90 (NO3) mg/l 40 R 2 = 0, Ploughed zornění půdy land v % (%)

19 Slope zones and vulnerable areas Different places in the catchment have different share on runoff formation and water quality In naturaly prone catchments water flow through three slope areas: 1) Recharge (infiltration) area water infiltrate through permeable soils 2)Transport area water move without recharge or discharge, 3)Discharge (accumulation) area water emerge into the recepient or cause waterlogging The biggest runoff portion originates in the recharge areas, these places have biggest effect on water quality in the catchment, so they act as vulnerable areas Proper delimitation of these vulnerable areas is necessary for applying successfull measures for improving the water quality.

20 Delimitation of vulnerable areas The most polular method is DRASTIC model with patameters: Depth to water, net Recharge, Aquifer media, Soil media, Topography, Impact of vadose zone media, and hydraulic Conductivity of the aquifer. In the Czech Republic delimitation according VSEU code (Valuated Ecological Soil Unit code relative soil infiltration capacity (Janglová et al., 2004) An improved method is,,delimitation of critical source areas of diffused agricultural pollution (Kvítek et al., 2008) And more complex: The synthetics map of subsurface water vulnerability (Novák et al. 2010, 2012).

21 Delimitation of vulnerable areas according to the VSEU code Categoryy

22 Depth of vadose zone Bedrock characteristics Syntetics map of vadose zone vulnerability

23 Synthetic map of soil and bedrock vulnerability vulnerability Category

24 The synthetics map of subsurface water vulnerability

25 Part 2: Landuse management and shallow subsurface water quality

26 Water quality in small sourcess of potable water is threatened by difused sources of pollution

27 Why to deal with the tile drainage? More than 25 % of agricultural land in the Czech republic has been drained (1,065 mil. ha). Drainage water often represent the only runoff from small agricultural catchments. Drainage has a large share of the total runoff and nutrient leaching out of catchments, especially during R-R events (summer storms, snowmelt). Drainage water allows us to study vadose zone processes without bias casused by surface runoff. Mechanism of drainage runoff and water quality formation is very similar to that of small sources of potable water in shallow aquifer.

28 Drainage runoff formation

29 Approach 1: Experiment with landuse grassing in part of recharge area in Dehtáře catchment Area: 57.9 ha Avg. temperature: 7,9 C Drained: 1977 Precipitation: 660 mm/year Tile drainage: 19 ha Bedrock: Paragneiss Spacing of tiles: 13 and 20m Soils: discharge area: Gleyed Depth of tiles: 1-1.6m Cambisols, Gleysols, Histosols Coordinates: N, recharge area: Modal, Ranker E and Arenic Cambisols

30 Selection the proper area for grassing Method of determination of relative soil infiltration vulnerability and the delineation of infiltration vulnerable areas. The method is based on the analysis of five-digit codes of valuated soil ecological units (VSEU - available as digital layers for the entire Czech Republic at a scale of 1:5 000) The VSEU code serves for the evaluation of soil characteristics according to the following criteria: main soil units, slope, exposure, skeletal character, and soil depth. Soil is classified into five relative groups according to its significance for the infiltration process, with category 1 corresponding to the maximum infiltration capacity.

31 It can be also based on the Synthetic map of soil vulnerability and vadose zone Category: Category:

32 Design of the experiment Monitored period: hydrological years (HR) , samples taken in one or two week step. Part of the recharge area with an area of 4.6 ha, has been grassed since the HR 2007 To evaluate the effects of this grassing, the whole time monitored was divided into two periods, period 1- before grassing (HR ) and period 2-after grassing (HR ). Six sites in the drainage system, with different land use in recharge and discharge areas, were chosen to be monitored for this analysis. All grassland in the catchment was fertilised by approximately 100 kg N/ha per season (mostly by urea and liquid manure). The arable land in the catchment was fertilised according to crop rotation (grains, potatoes and oilseed rape) in the amount of ca. 120 kg N/ha per season.

33 Design of the experiment

34 Results monthly flow weighted NO 3 concentrations Before grassing the RZ: Cfw surprisingly higher in sites K1, K2 and K4 with the permanent grassland in drained area (discharge zone) than in sites under arable land (K5, K6). Approximately one year after grassing (supposed mean residence time), the long-term course of NO 3 concentrations changed direction and became decreasing in sites with completely (K1, K2) or partly grassed recharge zone. In sites without land use change (K5, K6, K4), the nitrate Cfw trend remains increasing or the stagnation was found.

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36 Approach 2: statictical evaluation Study was carried out on 22 tile drainage systems Monitoring period Two regions: 1)the Švihov drinking water reservoir basin on the Želivka river 2) the Southern Bohemian foothills of the Šumava mountains. Examined drainage systems and related subcatchments were situated in crystalline complex with granite or paragneiss as parent rocks. The typical soil types were sandy-loam to loamy Cambisols and loam to clayloam gleyic Stagnosols Tile drainage systems were ostly built in slopes,

37 An example of a tile drainage subcatchment, with delineated infiltration-vulnerable areas and related land use types indicated

38 AR1-4: Arable land in soil vulnerable zones 1-4 GR1-4: Grassed land FR1-4: Forrests BU1-4: Built up land Results of PCA analysis

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40 Thank you for your kind attention Děkuji za pozornost