GIS och statistik vid dräneringsområdesvis kväveläckagebeskrivning i Halland
Physical geographyGeomorphologyGeographical information systemsNitrogen leechingRemote sensingLand useFjärranalysMarkanvändningCartographyPedologyNaturgeografiClimatologyGeomorfologiMarkläraKartografiKlimatologiEarth and Environmental Sciences
The last decades have shown increased nitrogen leeching from soil to water recipients. This is inSweden mainly due to over-manuring of agriculture land, effectivization of drainage systems and thedeclining extent of wetlands. The accumulated amount of nitrogen in water doesn?t only make itunsuitable for use by humans and cattle, but also decreases the biological diversity as well as negativelyaffect tourism and fish industry. In the most severe cases shallow maritime grounds can be completelydepleted of oxygen due to decomposition of the increased amount algae and plankton growth.This study have the aim to describe and quantify the nitrogen leeching from the Genevad drainagebasin, located in southern Halland, Sweden. The drainage basin (202.5 km2) has been found to be ofparticular interesting nature for nitrogen leeching studies. There are several spatially interestingcombinations of soil and land use with different nitrogen leeching characteristics. Also the lack of anysignificant point-source of nitrogen within the area is valuable. Use of IR-color air photography scannedat high resolution (2.5m) enabled accurate area assessments of land use, evaluated with use ofdifferentiated GPS. Field samples of nitrogen, conductivity, pH and discharge flow have been collectedfrom two different field visits. One field examination before the start of the agricultural season inMarch, and another field examination during the pre-summer season in May. Additional efforts werealso made to investigate the relationship between two measured variables; nitrogen and conductivity inwater-streams.The results show that soil and land use has significant impact on nitrogen leeching. There were alsonotable variations in the nitrogen leaching pattern between the samples from March and May. Theinvestigation of the relationship between nitrogen and conductivity showed significant and very strongcorrelation for both March and May samples as well as all samples pooled together. The daily nitrogenload from the drainage basin was calculated to 920 kg N/day in March and 320 kg N/day in May. Withuse of the significant correlation equation and cluster analysis the generalized average nitrogen load wascalculated to >0-3 kg N/ha year from woodlands on unsorted moraine, 1-8 kg N/ha year fromwoodlands on sorted moraine and 20-40 kg N/ha year for open and pasture lands on clay soils.A general conclusion is that the results from the observed nitrogen load and leeching pattern proved thatthe study area follows the established norm from other similar studies regarding soil and land use. Itwas also proved by the results from the statistical investigation that during particular biogeochemicalcircumstances the conductivity of stream water might be strongly correlated to the concentration ofdissolved nitrogen. Remote sensing, statistics and GIS were used as valuable tools for gathering,analyzing and handling large amounts of spatial information with high accuracy and integration.