Pilot implementation of WFD and creation of a tool for catchment management using SWAT: River Zglowiaczka Catchment, Poland

Abstract

Poland, like other EU countries, is obliged to implement the Water Framework Directive (2000/60/WE) by the end of 2015. The main objective of the Directive is to provide normative quality of all water resources (surface, underground and coastal sea waters). To reach this goal, reduction of water pollutant emission to the environment is needed. Our project focuses on pollution from agricultural sources which share in global pollution, which is high and growing. This is due to both intensification of agricultural activities and ignoring Agricultural Good Practice Code rules by farmers. In view of the above, this project is expected to provide analysis of selected catchments; especially those exposed to agricultural pollution risk, and propose adjustment strategies for new trends, still keeping in mind environment protection.

Our project concerns the area further called “sensitive area” (according to the rules of Regional Water Management Board in Warsaw). A part of Zglowiaczka river catchments in central Poland was defined as sensitive area (125.3 km²) where reduction of nitrogen and phosphorus run-off from agricultural land to water resources is especially needed. This is a typical agricultural district characterized by good soil quality (predominance of black swampy soil with deep and fertile humus layers). Due to this, it is the first and foremost high quality agricultural land, and almost forestless. The main topic of the research, with the use of the SWAT model, is to propose different means for reduction of migration of P and N to surface waters. Another problem is retention of water for actual and future irrigations. After model verification, calibration and validation, several climatic changes and reclamation strategies will be tested and simulated by the model to find the most effective and profitable solutions.

The project focuses on supporting administration and self-governmental organization in the implementation of effective strategies of catchments management based on a modeling approach. This method enables analysis of trends and early warning system against excessive pollution load. Enhancement of the ecological education level and activation of local population for implementation of EU directives are also very important factors.

Keywords

SWAT / modeling / nitrogen / nutrients / water management / agriculture / pollution

Introduction

Poland, like other EU countries, is obliged to implement the Water Framework Directive (2000/60/WE <FootNote>

Directive 2000/60/WE of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy

</FootNote>) by the end of 2015. The main objective of the Directive is to provide normative quality of all water resources (surface, underground and coastal sea waters). To reach this goal, reduction of water pollution in the environment is needed.

The main goal of the project is to help in the administration in the implementation of Water Framework Directive. The project is supported by Norwegian Financial Mechanism. Within the project operations the Virtual Institute of Sustainable Agriculture (VISA) (http://www.ibmer.waw.pl/wirz/amain.htm) is developing a tool which can enable assessment of catchments condition depending on different environmental situations and threats resulting from agricultural activities in the selected area.

The measures carried out within the project will enable development of computer tools which will facilitate the assessment of external factors that impact on the catchment area, and in consequence, they will lead to elaboration of the optimal management practices for the pilot catchment area. The applied method is expected to contribute to the minimization of both costs and the duration of recovery of good quality water resources. Moreover, the elaborated method will provide the administration authorities with an efficient tool to support proper management of catchment areas, which is very important in case of obligatory implementation of WFD requirements all over the country. The important issue is to provide the results in Polish, because English is not commonly used in local administration, especially in community level.

The main idea is to create such a tool, which can be implemented also in other agricultural catchments in Poland. That is why the model should be tested with rather simple data, easy to achieve in the whole country. The tool will be tested in one catchment as a pilot implementation and later popularized in the other areas. The final realization stage includes implementation and popularization of the program results, for example, free distribution of tools developed within the project tasks.

Study area

The catchment chosen for pilot implementation is Zglowiaczka river catchment. It is located in the central part of the Kujawy Region. This region is characterized by very high quality of soils, which is the reason why agriculture in this region is very intensive, in spite of unfavorable meteorological conditions. The annual precipitation in the Kujawy Region is the lowest in Poland. The average annual precipitation is 500 mm (600 mm for Poland), while during the vegetation period it is about 300 mm. Potential evapotranspiration in Zglowiaczka river catchment is 650 mm per year and in the vegetation period between 450-500 mm (Zlonkiewicz et al., 2007). On the basis of the results of subtraction between potential evapotranspiration and sum of precipitation, one could conclude about water deficits for agriculture and irrigation needs of grasslands and crops. The excess of precipitation related to potential evapotranspiration occurs during winter time (average 50 mm). During vegetation period, precipitation deficit is about 150-200 mm.

The Zglowiaczka river is a left tributary of Vistula river. The investigations were carried out in upper Zglowiaczka river, above the Gluszynskie Lake. The area of the catchment amounts to 125.3 km². The hydrografic network of this catchment is very poor and mostly formed by arable land drain system. About 75% of the whole catchment area is drained. Drainage system accelerates the circulation of water and nutrients in the catchment.

The landscape of Zglowiaczka river catchment is typical for intensive agriculture areas: poor, open and without larger forest complexes, meadows or grasslands. The area of catchment is characterized by very high quality of agricultural production space, due to high quality of soils. The dominant soil types are: black earth of Kujawy and gray-brown podzolic soils. That is the reason why on this area agricultural lands are the dominant form of land use (95% of total farms area included to NVZ). Grasslands occur only in small local land depressions (3.9%).

In 2004, almost the whole catchment was designated as Nitrate Vulnerable Zone (NVZ) according to Nitrate Directive of European Union (91/676/EEC <FootNote>

Council Directive 91/676/EEC of 12 December 1991 concerning the protection of waters against pollution caused by nitrates from agricultural sources

</FootNote>). The NVZs were designated on the basis of the results of water monitoring system. If the nitrate concentration in water was above the allowable value of 50 mg NO₃/dm³ and if the source of the pollution was or could be agriculture, the area was designated as a Nitrate Vulnerable Zone.

The state monitoring is conducted in three points in the upper Zglowiaczka river catchment. In each of these three points, nitrates concentration periodically significantly exceeds (mostly in spring and autumn) the allowable value of 50 mg NO₃/dm³ (Fig. 1). The highest average monthly values of nitrates concentration (1990-2007) occur in February, March and April, which indicates the impact of agricultural sources of pollution. During the rest of the year nitrates concentration is below the allowable value of 50 mg NO₃·dm^-3 (Fig. 2).

Model description

The processes leading to nitrogen and phosphorus migration into surface waters are very complicated. For over 30 years works have been carried out to develop model examples which enable proper description of this phenomenon. For catchment management purposes, the precision tools are needed for assessment of the processes over long periods of time, but not necessarily precisely describing daily pollution concentrations.

The SWAT model was chosen for the project—this is an acronym for Soil and Water Assessment Tool. It is a physically-based continuous-event hydrology model developed to predict the impact of land management practices on water, sediment, and agricultural chemical yields in large, complex watersheds with varying soils, land use, and management conditions over long periods of time (Neitsch et al., 2002).

This model divides the whole watershed into smaller parts having homogeneous land-use and soil conditions (HRU—hydrology response units). Then modelling processes are conducted in these smaller units. SWAT model simulates a complete cycle of nitrogen and phosphorus and takes into account changes in chemistry of these cycles (mineralization, decomposition, immobilization). SWAT is one of the most popular models and is used almost all over the World. The model can be applied as well for small catchments (Mishra et al., 2007) as well as for quite huge (Immerzeel et al., 2008). The history of the model as well as a description of the latest releases can be found on http://www.brc.tamus.edu/swat/.

Input data

The problem of modeling small catchments is the availability of data in proper resolution and accuracy. Usually, data for region and county are available but not always for all communes, not mentioning smaller units. In this project we are trying to use this kind of data, which will be available also in other parts of the country, to make the project as universal as possible.

SWAT model requires a great amount of data; meteorological data (in daily step), soil data, land management data, topographic data, and hydrologic data. These are compiled and analyzed with GIS. To supply reliable answers, the developed models must be fed with correct and exact data.

There were problems with old soil data, which was not very precise. In addition, old soil classification was not complementary with US classification. Therefore, new samples were taken and particle size distribution was analyzed. With former complex contours, a new map was developed conforming to the SWAT system.

The meteorological input data were collected from automatic weather stations for the 11-year (January 1996 to December 2006) simulation period by the Institute of Meteorology and Water Management. The study area is a small catchment (125.3 km²); therefore, daily values of rainfall, maximum and minimum temperatures, wind speed, and relative humidity were used only from one station located in Kołuda. There was a problem with daily solar radiation, because for Koluda there were no data for the same time period as the rest of the meteorological parameters. Therefore, we decided to use solar radiation values from two other nearest weather stations in Toruń and Koło. Additionally, default weather generator was replaced by user generator with parameters calculated for one weather station in Kołuda.

Topographical data were obtained from digital elevation model (DEM) which was obtained from SRTM mission (radar satellite imagery). This model is characterized by a pixel size of 90 m. In this particular area it was not enough for SWAT to determine streams; therefore, a generation of stream network was supported by additional vector layer of the stream network generated from topographical map.

Next part of the data is land-use. It is very hard to get the exact information about crops planted in the research area. The information is not open to the public. It is possible to get the information on the community level, but only about a part of the area, that is, selected farms from the surveys made by local administration. An assumption has been made that these farms are good representation of the whole area. According to this information, the main crops in the research area are: winter wheat (about 37% of area), spring barley, canola, corn, sugarbeet and vegetables (mainly onion) — all about 12% of area. On the basis of satellite image from Landsat, the range of arable land was determined. Landsat images are suitable for this purpose, because they are quite easily available for free for almost all areas. The spatial resolution of 30 m allows distinguishing between settlements, forests and agricultural land. The next step was to divide arable land into polygons representing different crops, so that the area of polygons is similar to the data from the local administration. This was made on the basis of Landsat image too. A three band composition (two infrared bands and one red) was used for this purpose (Miatkowski et al., 2006). The image is from the beginning of vegetation season (early May), so only parts of the fields are covered with vegetation. An assumption has been made that fields with vegetation are winter-wheat and canola fields. Others are without vegetation cover in this part of the year. According to this information, pixels covered with vegetation were divided into two groups: winter-wheat and canola, and other pixels into four groups: vegetables, spring barley, corn, and sugar beet. The result is shown in Fig. 3. This method allows us to avoid totally random distribution of the crops. It also gives a possibility of making a map more precise if there are more satellite images from different parts of the vegetation season.

The analysis of questionnaire distributed between farmers and data collected from commune offices brought the data concerning yields, amounts of applied fertilizers, and natural manure, as well as animal density. Prevailing agricultural practices and timing of agricultural operations (tillage, pesticide applications) were also studied.

Simulations

All the above mentioned data had been loaded to SWAT model and some simulations had been done. Proper calibration of the model is very difficult because of little amount of data. There are only some flow measurements and nitrogen and phosphorus concentration are measured once a month. During the project, some other measurements had been done and the results will be used later. Till now only general calibration has been made. Soil parameters have been adjusted, as well as curve numbers.

The accuracy of the model is tested only on the general water balance parameters and yields. These results are more than satisfactory. Part of the results is shown in Table 1. The values and their annual changes are as expected. The potential evapotranspiration (calculated using Penman-Monteith method) and water amount in soils is similar to measured. Also runoff rate in longer period is comparable to reality.

Manual approaches are still frequently used for calibration but they are tedious, time consuming, and require experienced personnel (Muleta and Nicklow, 2005); that is another reason for the restriction to such a basic calibration. This attempt gave a satisfactory result in other projects (Ndomba et al., 2008; Qiuming et al., 2006). Even with no calibration, the model can closely simulate monthly streamflow volume (Rosental et al., 1995). It is important to show that without complicated parameters adjustments the model can also be very useful in water management.

Reports tool

The output from SWAT consists of huge amount of data. Not all of them are necessary for water management. Also, not all of the parameters will be easily understandable for civil servants, who will need to deal with Water Framework Directive instructions and implementation. This is one of the reasons why we need a tool in results dissemination. Other reason is lack of English knowledge among local administration on lower levels. The tool which we wanted is a program with simple interface in Polish, which can work without any complicated GIS programs and be freely distributed. It should be possible to read the output from SWAT and show the most important results in a transparent manner. That was how SWATi was created. SWATi, which is an abbreviation from SWAT Interpreter (and is now a working name), is a program designed and written in C++ during the project. SWATi has the ability to read. dbf files generated by SWAT and automatically generate plots (Fig. 4) which are far clearer than very large tables, and easier in perception. In the upper part of the program window there is a table with chosen parameters from output files, it has additionally the names of all the columns (not only the abbreviation which sometimes may be hard to understand) and also translation of the names. There are also units for each column. From the table it is possible to select the column, which should be shown on the plot below. The table may be sorted according to date or subbasin number. The second important part of the program window is a smaller table on the left. There all subbasins are listed. From there it is achievable to choose one or more subbasins for the plot.

SWATi also has a possibility to read the shape files with watershed and subbasins and show results in a spatial manner (Fig. 5). The map can be animated and show how the situation changes during the months and years.

There is a possibility to export results in the form of pictures to MS Word or other editor. SWATi is still being changed and improved. There were some consultation done with local administration to see which parameters and functions will be especially important for them. There are still some new ideas to be tested and used in SWATi during the project.

Conclusions

Water Framework Directive is one of the most difficult directives to fulfil, and the European Commission has undertaken legal actions against several countries. This project focuses on supporting administration and self-governmental organization in the implementation of effective strategies of catchments management based on a modelling approach. This method enables analysis of trends and early warning system against excessive pollution load. Enhancement of the ecological education level and activation of local population for implementation of EU directives are also very important factors.

The costs of running the model for different scenarios are far lower than real implementation. So it is possible, using this tool, to create many changes in scenarios and choose the one which is most effective and least bothersome for farmers (Secchi and Gassman, 2007).

All analyses were not done with the metering equipment installed especially for the project. Data are from standard measurements made by institutions responsible for environmental monitoring. In addition, some satellite images have been used. This methodology is easily transferable to other parts of the country, and other sensitive areas.

SWAT model and our tool SWATi can be very useful for implementation of Water Framework Directive and local administration. As shown above, the tool is helpful also without very precise calibration and with data that can be quite easily acquired among the whole country. There is still a lot to be done in the project. But it is one of the first ideas in Poland to use modeling as a tool in water management, to find some general solutions.

References

[1] Immerzeel W W, Gaur A, Zwart S J (2008). Integrating remote sensing and a process-based hydrological model to evaluate water use and productivity in a south Indian catchment. Agricultural Water Management, 95: 11-24

[2] Miatkowski Z, Lewiński S, Kowalik W, Sołtysik A, Turbiak J (2006). Przydatność zdjęć satelitarnych Landsat TM do identyfikacji intensywnie odwodnionych siedlisk hydrogenicznych w rejonie KWB Bełchatów, Falenty: Wydaw. IMUZ

[3] Mishra A, Froebrich J, Gassman P W (2007). Evaluation of the SWAT model for assessing sediment control structures in a small watershed in India. Transactions of the ASABE, 50(2):469-478

[4] Muleta M K, Nicklow J W (2005). Sensitivity and uncertainty analysis coupled with automatic calibration for a distributed watershed model. Journal of Hydrology, 306: 127-145

[5] Ndomba P, Mtalo F, Killingtveit A (2008). SWAT model application in a data scarce tropical complex catchment in Tanzania. Physics and Chemistry of the Earth, 33: 626-632

[6] Neitsch S L, Arnold J G, Kiniry J R, Williams J R, King K W (2002). Soil and Water Assesment Tool Theoretical Documentation. Texas Water Resources Institute, College Station, Texas

[7] Qiuming C, Connie K, Yinhuan Y, Yong G, Shengyuan Z (2006). GIS modeling for predicting river runoff volume in ungauged drainages in the Greater Toronto Area, Canada. Computers & Geosciences, 32: 1108-1119

[8] Rosenthal W D, Srinivasan R, Arnold J G (1995). Alternative river mmanagement using a linked GIS-Hydrology model. Transaction of the ASAE, 38(3): 783-790

[9] Secchi S, Gassman P W (2007). The cost of cleaner water: Assessing agricultural pollution reduction at the watershed scale. Journal of Soil and Water Conservation, 2007:1-2

[10] Złonkiewicz M, Łabędzki L, Gruszka J (2007). Agricultural irrigation program for Kujawsko-Pomorskie Voivodship, Bydgoszcz

RIGHTS & PERMISSIONS

Higher Education Press and Springer-Verlag Berlin Heidelberg