Gebietsbilanzen bei unterschiedlicher Landnutzung Tentative nitrogen budgets of lower Krka and upper river basins in M. VESELIC, M. PINTAR und A. DROLC

Abstract normal pattern of the alpine streams, European areas with a developed agri- cultural activity the groundwater nitrate Within a targeted research project aimed since some of them show just the oppo- concentration exceeds 25 mg/l and in at definition and verification of a metho- site reaction. 22% of them it exceeds 50 mg/l, actual- dology for the determination of areas, We may conclude, that the applied me- ly prescribed as a drinking water accep- vulnerable to nitrate pollution, and of the thodology of river basin total nitrogen tance limit. Such areas can unfortunate- respective remedial measures according budget determination has proven to be ly be found also in Slovenia. to the EU nitrate directive 91/676/EEC, reliable enough with a good potential to tentative nitrogen budgets for two cha- get even more precise. However the river Slovene territory is from a regional hy- racteristic river basins were elaborated water quality monitoring should have a drologic aspect divided between the Da- in Slovenia. better discharge coverage especially with nube Basin and the Mediterranean Basin. On the European Scale these were defi- In the case of lower Krka river, it was respect to high discharge periods. To ned as eutrophic areas. In a search of a found that the total nitrogen concentra- achieve a better internal regionalisation policy complying with the Aquis Com- tion load seems to be discharge indepen- of the analysed river basins with respect munotaire, the Slovenian Ministry of dent, i.e., high discharge periods convey to the nitrate pollution and vulnerabili- Environment and Physical Planning has correspondingly higher quantities of to- ty, the existing data structure must be decided to develop and to verify a me- tal nitrogen. This might eventually be a made more appropriate. By now, this can thodology for the determination of ni- general case for the lowland karst stre- only be achieved on basis of related spe- trate pollution vulnerable areas. A deter- ams. Further, it was found that for the cific studies and data collection. mination of a set of measures should lower Krka river basin, the nitrogen bud- The study has also demonstrated, that the enable Slovenia to comply with the EU get could be determined precisely enough population may be a bigger source of nitrate directive. A targeted research pro- to fit the precision margins imposed by total nitrate pollution as readily believed. ject, designed to respond to the above the Krka river nitrogen inflow at its upst- While this extent is relatively obvious for goals, was financed jointly by Ministries ream edge and nitrogen outflow at its urban areas, it is less clear for disperse of Science and Technology and of Envi- downstream edge. But it was found out settlement. No data are available which ronment and Physical Planning of the also, that these precision margins are would enable to check the nitrogen re- Slovene Government and carried out by rather loose due to the relatively high duction efficiency of the existing septic a consortium of Slovene research insti- upstream edge nitrogen load of the river, tanks and other equivalent sanitary faci- tutions. Within this paper, the authors try allowing the analysed river basin nitro- lities. So, part of the pollution deriving to present the main lines of the applied gen budget to fit easily. from disperse settlement is actually methodology and its results and draw For the upper Savinja river basin it was being attributed to agriculture. attention to some of the emerged questi- found that the nitrogen budget can not ons that need to be further researched. be determined precisely enough. Sever- Introduction al sources of error may have to be chek- In the European Union is the protection Methodology ked: nitrogen import to groundwater of water resources with respect to the On the basis of the water nitrate content from septic tanks and from agriculture, nitrate pollution regulated by the nitrate data, resulting from the existing Slove- Savinja river basin outflow and nitrogen directive (91/676/EEC). This directive ne water quality monitoring network, load at high discharge. Theoretically, requires a definition of nitrate pollution vulnerable areas were determined accor- discharge related changes in pollution vulnerable areas, where agricultural ac- ding to the criteria of the EU nitrate di- load are connected to the relative im- tivity and use of fertilisers have to be rective (91/676/EEC). It was observed portance of point and diffuse pollution restrained or controlled due to a proba- that on most of the Slovene flatland are- sources. Given the structure of the ni- ble transfer of excessively applied nu- as, formed of Pleistocene gravel depo- trate budget of the upper Savinja river tritients to groundwater and surface wa- sits, groundwater nitrate content in 10- basin, with agriculture being the most ters. Elevated nitrate water content and 50% of cases exceeds the above 50 mg/ important, diffuse pollution sources observed eutrophycation of surface wa- l nitrate content limit. They should be should prevail. Consequently, high di- ter bodies are used as primary criteria therefore defined as nitrate pollution vul- scharge waters should not be less but for the determination of such areas. nerable areas. According to the 50 mg/l eventually even more charged. It remains According to a European environment nitrate content limit criteria, surface to be checked whether this may be the status report (EEA, 1995) in 87% of waters in Slovenia can not be defined as

Autoren: Univ. Prof. Dr. Miran VESELIC, IRGO, Institute for mining, geotechnology and environment, Slovenceva 93, SI-1000 ; Ph. D. Marina PINTAR, Bio-technical Faculty of the University of Ljubljana, Jamnikarjeva 40, SI-1000 Ljubljana; Andreja DROLC, National Institute of Chemistry, Hajdrihova 19, SI-1000 LJUBLJANA

9. Gumpensteiner Lysimetertagung, 24. und 25. April 2001 Bundesanstalt für alpenländische Landwirtschaft Gumpenstein, A-8952 Irdning 101 M. VESELIC, M. PINTAR und A. DROLC nitrate pollution vulnerable. With respect the atmosphere, diffuse, uncontrolled ! experimentally determined values to eutrofication, the controlling factor is point releases of waste waters, at- from the analysed region, actually the phosphorus content. This, mospheric deposition. " values, extrapolated from state to re- however, is not a matter of concern of The most important processes involving gional level, the EU nitrate directive. nitrogen compounds are: # values, determined experimentally In order to understand the nitrogen com- ! nitrification and de-nitrification of in a comparable region, pounds dynamics within the environ- nitrogen compounds, $ data from literature, and ment and the effects of relative pollut- " autopurification through reactivati- ion abatement measures, a methodolo- % expert opinions. on of organic compounds, and, gy of the nitrogen budget determination Two river basins were selected to test the at a river basin scale was elaborated # nitrogen compounds assimilation. proposed methodology and to check (DROLC, 1998). Nitrogen compounds Due to the dynamics of these processes whether the existing data structure at dynamics within a river basin was stu- can the nitrogen compounds emission to state and regional level as well as the died by means of a nitrogen material flow imission ratio serve only as an estimate actual scheme of water quality moni- analysis. By linking sources, paths and and rough approximation of the actual toring allow us to determine and to sinks of the individual substances, this state. monitor the existing nitrate and nitro- method enables within a river basin the In order to determine the budget of ni- gen loads. Further, they should ena- identification of the main pollution trogen compounds, human activities were ble a test of their adequacy of control sources. The results of an analysis of divided into the following processes: of the respective pollution abatement material flows, coupled with the results measures. The position of these river ! process ”waste waters”, and, of surface water quality monitoring, en- basins within Slovenia is shown in Fi- able a comparison of emission values " process ”agriculture” with sub-pro- gure 1. cesses ”farm” and ”arable land”. At- (pollution sources) with the imission The lower Krka river basin, situated bet- mospheric deposition and natural back- values (experimentally determined actu- ween the town of and ground were integrated into the process al pollution load within the river). Ni- Krka’s outflow to river, was selec- ”agriculture”. trogen is from point and diffuse sources ted because it is nutritient loaded and transferred into surface waters through Also distinctive constituents of the en- therefore urgently needs some effective different paths and transport media (soil, vironment, involving each a multitude of pollution abatement measures. It has a air, water). Due to this, its budget has to processes, were considered as individu- typical set of human activities (urbani- include two ecosystems – aquatic and al macro-processes, i.e., ”process surface sation, industry, agriculture). Novo Me- terrigenous. waters”, ”process groundwater”. sto at its upstream edge is a strongly ur- Human activities (processes), constitu- Material flow analysis is methodologi- banised and industrialised regional cen- ting main pollution sources within a re- cally based on the data, which, by their tre. Krka river is a typical karst stream gion, were grouped according to activi- origin, fall into the following categories: of a hilly area, with upper Krka having ty type (population/settlement, industry, agriculture, atmospherical deposition and natural background). Main water N bodies (surface waters, groundwater), re- presenting the study subjects, were also defined. By doing this, we can display consequences of individual human acti- vities, process interaction and impacts to the environment. In a river basin nitrogen Sa vin budget determination we have considered: ja ! activities, emitting nitrogen com- pounds into waters, and, Sava " emission or transport pathways into environment (direct release of waste wa- ter, leakage, erosion, evaporation, at- K r mospheric deposition, …). ka As nitrogen pollution sources are either point or diffuse, it is important to deter- mine the main transport pathways with respect to these sources. They are: ! point sources - direct releases of wa- ste water, and, " diffuse sources - erosion and diffu- River basin of upper Savinja se surface flow, soil leaching and per- colation to groundwater, evaporation to Figure 1: Situation of lower Krka and upper Savinja river basins

102 9. Gumpensteiner Lysimetertagung, BAL Gumpenstein Tentative nitrogen budgets of lower Krka and upper Savinja river basins in Slovenia

sub-basins, where basins of its tributa- ries and of specific Savinja river sectors were also analysed as individual budget entities. In this way, we have performed a regionalisation of the river basin.

Results With respect to the nitrogen budget de- termination, the import of the nitrogen into the basin by the Krka river at the basin’s upper or inflow edge and its ex- port by the Krka river at its lower or out- flow edge had to be determined to set the basin’s boundary conditions. For this, the data on Krka river discharge data and on its water quality from the state’s mo- nitoring network were analysed, where 1996 was taken as a reference year. The Figure 2: Krka river discharge at Podboèje (from DROLC, 1998) hydrograph of river Krka at its river basin outlet for the analysed period is display- ed on Figure 2. In the case of lower Krka river, it was found that the total nitrogen concentra- tion load seems to be discharge indepen- dent, i.e., high discharge periods convey correspondingly higher quantities of to- tal nitrogen. This might eventually be a general case for the lowland karst stre- ams. Figure 3 presents the obtained re- lation between nitrogen load and Krka river discharge. As previously explained, human activi- Figure 3: Nitrogen load versus discharge for river Krka (from DROLC, 1998) ties were for the purpose of the lower Krka river basin nitrogen budget deter- nearly exclusively carbonate watershed The upper Savinja river basin was selec- mination divided into processes ”waste and the corresponding discharge condi- ted for its variety of environmental con- waters” and ”agriculture” with sub-pro- tions. Environmental conditions in the ditions ranging from pristine alpine and cesses ”farm” and ”arable land”. lower Krka river basin range from hilly forested pre-alpine to heavily agricul- With respect to the ”waste waters” pro- to a river plain and from pristine forest turally loaded and urbanised river val- cess, it was considered that: to intensively cultivated and urbanised. leys and plains. Alpine and pre-alpine ! the analysed basin has 52.300 inha- The method applied is based on the ana- areas are built preponderantly from car- bitants (yielding 12 g/person/day of N), lysis of total nitrogen flows within the bonates. Hilly regions are mostly formed river basin and is being often used for of little pervious Tertiary strata. Valleys " 17.400 of these are connected to the nitrogen budget elaboration, cf. Upper and plains are filled with Pleistocene wastewater treatment plant, Austria (DROLC, 1998). Point and dif- gravel deposits. Savinja river and its tri- # this plant receives 90% of nitrogen fuse nitrogen sources are identified for butaries have a strong flooding potenti- input from population and 10% from the purpose, as well as the media of ni- al and are typical alpine and pre-alpine industry, trogen transport and the transport paths streams. Their water quality varies in $ nitrogen content removal efficiency and processes. A river basin is regarded time and space, ranging from excellent of the wastewater treatment plant is 36%, as a single budget entity, with human ac- to poor. Pleistocene gravel aquifers in % Novo Mesto sewage system loss to tivities as sub-budget categories. By this, valleys and plains are important drinking groundwater is 19%, the environmental impacts of various hu- water sources and locally heavy nitrate man activities can be assessed as well as polluted. At least locally, remedial mea- & of 34.800 inhabitants using septic interaction and possible nitrate polluti- sures against nitrate pollution must be tanks, 3.500 transfer sewage to waste- on reduction issues. No internal subdi- implemented. The same nitrogen budget water treatment plant, 300 release sewa- vision of a river basin according to its methodology as for the lower Krka river ge directly to surface flow and the rest natural conditions, human activities, or basin was applied also here. However, let their septic tanks leak, pollution loads and other constraints is due to its complex structure, the upper ' 60% of the nitrogen that leaks from involved. Savinja river basin was subdivided into septic tanks reaches groundwater,

9. Gumpensteiner Lysimetertagung, BAL Gumpenstein 103 M. VESELIC, M. PINTAR und A. DROLC

INDUSTRIJA PREBIVALSTVO

direktni izpust čistilna naprava direktni izpust čistilna naprava greznice 0 t/l 194,3 t/l 1,3 t/l 77,1 t/l 137,1 t/l

ODPADNE VODE

direktni izpust direktni izpust iztok iz ČN iztok iz ČN greznice aktivno blato (ind.) (preb.) (ind.) (preb.) pronicanje 0 t/l 1,3 t/l 75,5 t/l 49,4 t/l 27,4 t/l

POVRŠINSKE VODE PODTALNICA ODPADKI

Figure 4: Process ”waste water” for the lower Krka river basin ( nitrogen content removal efficiency Results of the above processes and sub- upstream edge nitrogen load of the river, of the industrial wastewater treatment processes and of the nitrogen import and allowing the analysed river basin nitro- plant is 61%. Figure 4 shows this pro- export can be summarised into the an- gen budget to fit easily. cess. nual nitrogen budget of the lower Krka For the upper Savinja river basin the With respect to the process ”agriculture” river basin for the year 1996, displayed upstream edge inflow is nil and only the sub-processes ”farm” and ”arable land” in the Figure 6. downstream edge outflow is to be consi- have to be considered separately. Accor- From the above, it can be concluded that dered. The already known material flow ding to statistical data, the river basin the nitrogen input from ”surface waters analysis was carried out, based on the surface consists of 34% of arable land, inflow”, ”waste waters”, ”groundwater”, data specific to the Upper Savinja river 14% of non-arable land, 46% of forests ”agriculture” and ”atmospheric deposi- basin. We summarise here only the an- and 6% of areas without vegetation. tion” amounts in the case of the lower nual nitrogen budget of the upper Savinja According to the same data, its farms Krka river basin in year 1996 to 3.438,5 river basin for the year 1998, as issued breed 286 horses, 17.735 cattle, 21.188 tons of N/annum. All the nitrogen emit- from all the analysed processes and sub- pigs, 991 sheep and 333.562 chicken. ted within the lower Krka river basin processes and from the nitrogen export The nitrogen application via fertilisers amounts to 496.8 tons of N/annum. Data at the river basin’s outlet. The results are and animal manure to the arable land is on surface waters outflow show for the presented on Figure 7. considered to be at the mean Slovene same period an export of 3.207,8 tons From the above, it can be concluded that level. Atmospheric deposition is deter- of N/annum. With Krka river’s annual the nitrogen input from ”waste waters”, mined on the basis of data from Novo discharge determination error being 5% ”groundwater”, ”agriculture” and ”at- Mesto monitoring station. Atmospheric (which is a fairly low value in standard mospheric deposition” amounts in the nitrogen fixation is taken 40 Kg N/ha/ engineering practice) and no nitrogen case of the upper Savinja river basin in year on basis of the crop production water load determination error occur- year 1998 to 3.000,6 tons of N/annum. structure. Within the sub-process ”farm” ring, the error margin for lower Krka All this nitrogen is emitted within the is nitrogen transferred in fertilisers and river basin’s nitrogen budget is of the river basin, with agriculture (annual in- animal manure from ”farm” to the ”ara- order of 300 tons of N/annum. The ob- put of 2.414,6 tons of N/annum) being ble land”, in gas losses from ”farm” to served difference within the nitrogen by far the strongest nitrogen source and the atmosphere and in part of liquid export and import values is 230 tons of groundwater (annual transfer of 2.665,2 manure from ”farm” to surface waters. N/annum. We may conclude that the tons of N/annum) its strongest vehicle. Within this frame is, 15% of all nitrogen budget could be determined precisely Data on surface waters outflow show for produced at the farm released through enough to fit the precision margins im- the same period an export of 2.636,9 tons gas losses to the atmosphere and 1% of posed by the Krka river nitrogen inflow of N/annum. Similarly, with Savinja all animal manure produced at the farm at its upstream edge and outflow at its river’s annual discharge determination released as liquid manure to surface wa- downstream edge. But it was found out error being 5% at one measuring point ters. Figure 5 shows this sub-proces- also, that these precision margins are only and no nitrogen water load deter- ses. rather loose due to the relatively high mination error occurring, the error mar-

104 9. Gumpensteiner Lysimetertagung, BAL Gumpenstein Tentative nitrogen budgets of lower Krka and upper Savinja river basins in Slovenia

ATMOSFERA

plinske izgube- fiksacija dušika denitrifikacija atmosferska plinske izgube- kmetija 880,0 t/l 550,0 t/l depozicija kmetijska zemlj. 278,0 t/l 185,4 t/l 234,7 t/l

živinska gnojila 1564 ,7 t/l

KMETIJE kmetijski pridelki KMETIJSKA ZEMLJIŠČA

umetna gnojila 1135,2 t/l

direktni izpusti erozija izluževanje 15,8 t/l 26,9 t/l 220,0 t/l

POVRŠINSKE VODE PODTALNICA

Figure 5: Process ”agriculture” for the lower Krka river basin

ODPADNE VODE

direktni izpust direktni izpust iztok iz ČN iztok iz ČN (ind.) (preb.) (preb.) (ind.) 0 t/l 1,3 t/l 49,4 t/l 75,5 t/l

erozija podzemni tok 26,9 t/l 123,7 t/l PODTALNICA

izpust živ. gnojil KMETIJSTVO 15,8 t/l erozija POVRŠINSKE VODE 5,5 t/l ATM. DEP . vtok - iztok -površinske površinske vode vode 2941,7 t/l IMPORT 3207,8 t/l EKSPORT

Figure 6: Nitrogen budget of the lower Krka river basin for the year 1996 gin for upper Savinja river basin’s nitro- fit the precision margins imposed by the lower Krka river basin. Observed nitro- gen budget is of the order of 130 tons of Savinja river nitrogen outflow at its gen budget error shows that this is not N/annum. The observed difference wit- downstream edge. the case. Several sources of error may hin the nitrogen export and import valu- No nitrogen import from inflowing sur- have to be checked: es is close to 364 tons of N/annum and face streams exists in the upper Savinja ! nitrogen import to groundwater from is well above the desirable error margin. river basin and we expected to be able septic tanks (maybe overestimated); We may conclude that the budget could to test the method of material flow ana- " import of nitrogen from agriculture not be determined precisely enough to lysis more precisely as in the case of the (may also be overestimated),

9. Gumpensteiner Lysimetertagung, BAL Gumpenstein 105 M. VESELIC, M. PINTAR und A. DROLC

ODPADNE VODE

direktni izpust direktni izpust iztok iz ČN iztok iz ČN (ind.) (preb.) (preb.) (ind.) 0 t/l 1,3 t/l 49,4 t/l 75,5 t/l

erozija podzemni tok 26,9 t/l 123,7 t/l PODTALNICA

izpust živ. gnojil KMETIJSTVO 15,8 t/l erozija POVRŠINSKE VODE 5,5 t/l ATM. DEP . vtok - iztok -površinske površinske vode vode 2941,7 t/l IMPORT 3207,8 t/l EKSPORT

Figure 7: Nitrogen budget of the upper Savinja river basin for the year 1998 budget determination has proven to be References reliable enough with a good potential to DROLC, A., 1998: Integriran prostop k ocenjevan- get even more precise. However the river ju virov dušikovih in fosforjevih spojin v po- water quality monitoring should have a reèju. Dokt. disertacija, Univerza v Ljubljani, Point and diffuse sources better discharge coverage especially with Ljubljana. are important respect to high discharge periods. To EUROPE FAILING ON NITRATES, 1997: Water Concentration achieve a better internal regionalisation Quality International, November/December Diffuse sources prevail of the analysed river basins with respect 1997. to the nitrate pollution and vulnerabili- EUROPEAN ENVIRONMENT AGENCY, 1995: Point sources prevail ty, the existing data structure must be Europe’s Environment, Urednika D. Stanners Discharge made more appropriate. By now, this can in P. Bourdeau, Copenhagen. only be achieved on basis of related spe- Figure 8: Load to discharge relation for FLECKSEDER, H., 1992: A nitrogen balance for cific studies and data collection. Austria, Water Science and Technology, 26, surface streams (from DROLC, 1998) The study has also demonstrated, that the 1789 - 1795. # Savinja river basin outflow (it may population may in some cases be a big- GERRITSE, R. G., J.A. ADENEY and J. be higher); ger source of total nitrate pollution as HOSKING , 1995: Nitrogen losses from a do- readily believed. While this extent is re- mestic septic tank system on the Darling pla- $ nitrogen load at high river dischar- teau in Westeren Australia, Water Research, 29, ge (it may be higher). latively obvious for urban areas, it is less 2055-2058. Theoretically, as shown by Figure 8, di- clear for disperse settlement. No data are LAMPERT, C., I. REINER., E. GLENCK, M. scharge related changes in pollution load available which would enable to check ZESSNER, R. FENZ und P.H. BRUNNER, are connected to the relative importance the nitrate reduction efficiency of the 1995: Nutrient Balances for Countries, of point and diffuse pollution sources. existing septic tanks and other equiva- Methodology on Materials Accounting, TU Wien, IWAG, Wien. Given the structure of the nitrate budget lent sanitary facilities. So, part of the NUTRIENT BALANCES FOR DANUBE COUN- of the upper Savinja river basin, with ag- pollution deriving from disperse settle- ment is actually being attributed to agri- TRIES, 1997: Final report, Project EU/AR/ riculture being the most important, diffu- 102A/91, Institute for Water Quality and se pollution sources should prevail. Conse- culture. Waste Management, University of technolo- quently, high discharge waters should not be gy, Vienna, Department of Water and Wa- less but eventually even more charged. It Acknowledgement stewater Engineering, University of Techno- logy, Budapest. remains to be checked whether this may be The authors express their gratitude to the normal pattern of the alpine streams. both the Ministry of Science and Tech- THE NITRATES DIRECTIVE, 1991: OJ No L 375, p.1, 31. 12 1991. nology and the Ministry of Environment Conclusion UNITED NATIONS, 1992: MIC Commissi- and Physical Planning of the Slovene on for Europe, Geneva, Protection of In- We may conclude, that the applied me- Government for having supported this land Waters against eutrophication, New thodology of river basin total nitrogen study under the contract V1-0231-99. York.

106 9. Gumpensteiner Lysimetertagung, BAL Gumpenstein