Scientific Journal of Riga Technical University Environmental and Climate Technologies DOI: 10.2478/v10145-010-0029-0 2010 _________________________________________________________________________________ Volume 5 Seasonal Characterisation and Trends Study of Nutrient Concentrations in Surface Water from Catchments with Intensive Livestock Farming Laima Berzina, Department of Environmental Engineering and Water Management , Latvia University of Agriculture Ritvars Sudars, Latvia University of Agriculture Department of Environmental Engineering and Water Management, Latvia University of Agriculture Abstract – Temporal changes in observed nitrogen and In addition, nutrient concentrations variation in agricultural phosphorus losses to surface water were studied in 3 agricultural catchments surface water is examined and a trend analysis is catchments in order to evaluate the achievement of water carried out in order to investigate whether the proposed protection targets in Latvia. The aim of this study is to investigate the water quality measures in high density livestock farming changes in agricultural practices have affected nutrient catchments. Long-term monitoring data (years 1996–2008) of concentrations in the surface water. The study consists of water quality used in the analysis show a high annual and comparing seasonal nutrient concentrations in surface waters monthly variability of nutrients. The results demonstrate little or and the detection and quantification of the water quality trends no reduction of nutrient concentrations in surface water. The in surface water nutrient concentrations by the Mann–Kendall results suggest that water protection measures for agricultural Seasonal Test and the Sens Slope Estimator. Understanding production need to be further intensified. the status of surface water and nutrient trends in streams and Keywords – Livestock farming, nutrients, point source surface conditions that affect them was possible thanks to the water pollution, seasonality, trends. agriculture run-off monitoring project provided by the Department of Environmental Engineering and Water Management, Latvia University of Agriculture. I. INTRODUCTION Farming with high livestock density can lead to local II. MATERIAL AND METHODS manure surpluses, which can result in surface water pollution The study is based on the long-term (1996-2008) nutrient problems in rural regions. During the last years there is a concentration in surface water observation data from three tendency in Latvia to increase the number of big animal farms, catchments (Bauska, Ogre, Auce) included in the national thereby livestock concentration in specific areas can cause network for the agriculture run-off monitoring programme nutrient pollution from point sources and subsequently prevent designed to cover point source agriculture pollutant the fulfillment of objectives of the Water Framework investigation. In all agricultural catchments, the amount of Directive (WFD, 2000/60/EC) and the Nitrates Directive livestock is remarkable (more than 250 LU) and most of the (91/676/EEC). According to the assumption that point source cultivated land is under cereal crop cultivation, which is pollution is usually concentrated, it is considered as the most common in southern and central Latvia. The main significant contamination source [1]. Generally, the origin of characteristics of all catchments are presented in Table 1. point source pollution is from one location, and thereby runoff Results are compared with the diffuse source agricultural from a feedlot or overflows from hog lagoons and slurry pollution monitoring results to provide an overall view of the deposition on fields near streams, are examples of agricultural major water quality characteristics occurring in surface waters. point sources of contamination. However, possible source of The long term point source and diffuse source database is such types of pollution in agriculture can also be associated maintained by the Latvia University of Agriculture (LLU). with a high number of livestock units or with high animal TABLE 1 density (livestock units (LU) per ha) in a farm. According to CHARASTERISTICS OF CACHMENTS HELCOM (Helsinki Commission - Baltic Marine Area, Known point Environment Protection Commission) guidelines, the Catchment Soils Land use Farm type ha sorce inputs agricultural area or farm should be considered as a hot spot, if pig farm, slurry sandy grain it is a watershed with an animal density higher than 1.5 LU per Auce 60 established application on loam farming ha or an area with large animal farms with more than 250 LU in 1990 30 ha that cannot demonstrate appropriate fertilizers and manure pig farm, slurry grain Bauska 800 silt, loam established application on storage or application [2]. farming The aim of the study is to estimate surface water quality in in 1970 50 ha pig farm runoff from the territories with a high number of livestock unit farms by silty clay moderate Ogre 300 closed in old slurry describing water quality parameters (total nitrogen, total loam farming 1992 lagoons phosphorus, nitrates) variation with regard to time and season. 8 Scientific Journal of Riga Technical University Environmental and Climate Technologies DOI: 10.2478/v10145-010-0029-0 2010 _________________________________________________________________________________ Volume 5 The grab water samples from draining ditches were The analyzed water quality parameters show striking analyzed for total phosphorus (P tot. ), total nitrogen (N tot. ) and seasonal variations for different reasons. According to the nitrate nitrogen (NO 3-N). Water quality parameters are tested research [3, 5, 7, 8, 10], nutrient concentrations vary in accordance with standard methods LVS EN ISO 11905-1, throughout the year, largely due to the response to changes in LVS EN ISO 13395 (N tot. ) and LVS EN ISO 15681-1 (P tot. ). precipitation, ground water levels and flow rates. Some of A seasonal analysis including an evaluation of seasonal them depend on discharge and seasonality; but same are patterns of nutrients in surface water are conducted for two magnified by agricultural activities. The Mann-Whitney U test seasons (summer and winter) by Mann–Whitney U test and used to compare nutrient concentrations in the summer and for twelve season (monthly data) by Kruskal-Wallis. The winter months according to the Nitrate Directive (winter seasonal patterns are also evaluated using box plots to provide period: October – March, summer or vegetative period: April a general overview of the trends and calculating seasonal – September) also affirms statistically significant nutrient indices. The statistical significance of nutrient trends are concentrations differences (all p-values less that 0.02) between determined by a Seasonal Kendall test . This test is suitable for these two periods in all catchments. However, on the practical water quality data because it requires no assumption of level, the Ptot. median values in the summer and winter are very normality that is very important to investigate point source close in the Auce catchment. Figure 1 displays the median pollution [4]. It consists of the sum of the individual MKs values of nutrient concentrations for the summer and winter values for each cyclic period, thereby removing the seasonal months separately and compares results with long term (1996- component. The magnitude of statistically significant trends 2008) diffuse pollution monitoring data. This examination of was estimated according to the Seasonal Kendall slope data shows that N tot. values tend to be higher in the winter estimator. while P tot. values are higher in the summer months. Nitrogen concentrations in agricultural streams can be high during the III. RESULTS AND DISSCUSION winter in connection with high water flows and the low The basic descriptive statistics of nutrient concentrations in intensity of biological processes, however more phosphorus surface water regularly conducted over a period (1996–2008) are transported during storms. Exploration of data also at 3 catchments are summarized in Table 2. The results includes comparison of observed values with long term demonstrate that nutrients in surface water tend to be highly agricultural diffuse pollution monitoring results. Observed N tot. values in the Bauska and Auce catchments are clearly higher variable. The highest values as well as the high variability for -1 all nutrients are observed in the Bauska catchment which is than the Ntot. concentrations (median 7.2 N tot. mg L ) recorded characterized by high animal density and the application in the high input agriculture run-off monitoring database. (utilization) of manure. Despite the high manure rates applied However, the median values of N tot. in Ogre decrease down to the level of medium input agriculture run-off long term on the fields, the median nitrate concentrations in all -1 -1 median value (3.3 N tot. mg L ) in the winter, but in the catchments are below the threshold value 11.3 mg L of NO 3- summer N tot. concentration in the Ogre catchment reach the N established by the Nitrate Directive. However, high -1 value (1.4 N tot. mg L ) typical for the low input agriculture concentration of total nitrogen (N tot. ) and total phosphorus conditions in Latvia. Median values of P tot. are two and more (P tot. ) are documented. P tot. is the parameter that shows the times higher as the observed phosphorus concentration in high greatest degree of variation throughout the studied period in -1 all catchments except