Browsing by Author "Nenonen, Päivi"

Urbanization effects on hydrology and water quality on catchment area because of the land use change. Construction sites in catchment causes water quality problems. Waters from construction sites are usually led straight to watercourses without any purification actions. This has also been the practice at residential construction site in Suurpelto, Espoo. The aim of this study is to evaluate how discharge, water quality and loadings have changed during construction at Suurpelto. This research is the second part of the 'Kaupunkirakentamisen vaikutukset Lukupuron hydrologiaan ja veden laatuun' (LUPU) -project which is conducted by the University of Helsinki and city of Espoo. The observation period begins from the year 2006 and has divided into three sections. The first section represents time before construction. At the second section (Construction phase 1) construction work has started, and streets and municipal infrastructure are being built. During the third section (Construction phase 2) residential construction is very intensive and municipal infrastructure is expanding to new areas. The purpose of this study is to compare these sections with each other and report differences between water quality, discharge and loadings. Spearman's rank correlation coefficient is used to evaluate the dependences between water quality variables. Wilcoxon signed rank test is used to discover statistical significance in load variations. This study was carried out by analyzing 22 different variables: Discharge, electrical conductivity and pH was measured by automatic water quality probe. Suspended solids, nutrient concentrations (total phosphorus and total nitrogen) and dissolved substances including metals (total dissolved solids, sodium, potassium, magnesium, calcium, fluoride, chloride, sulphate, chromium, iron, nickel, chopper, arsenic) were measured in laboratory. The hypothesis of this study is that water quality has changed statistically significantly as a result of land use change in the catchment. Another hypothesis is that loadings have increased. Results of this study indicate that loadings of suspended solids, total phosphorus and iron as well as discharge are statistically significantly increased because of construction works. However, electrical conductivity has decreased because of increased discharge. For instance suspended solid load has sixfold in a year, total phosphorus has fourfold and iron load has increased even 11 -fold, when comparing construction phase 2 and time before construction. The growth of discharge has been particularly large in construction phase 1. Between construction phases 1 and 2 the change has been minor and statistically insignificant. Hence, the most significant changes have occurred during construction phase 1 and for instance total phosphorus loading has decreased during construction phase 2. Effects of construction is depended on other human activity and natural causes such as dredging of the channel, fertilization of the fields, weather conditions and the soil type. If one want to decrease the negative effects that construction work causes to water quality, one have to consider new ways to process waters flowing from construction area. Possible new means have been already considered during the restore planning of Lukupuro in spring 2013. Dredging took place in the new part of the Lukupuro main channel and effects were very significant to water quality. Based on the knowledge we have now it is important to consider pros and cons of relocating the channel in the future.