Time of concentration, Tc, is defined as time elapsed from the beginning of rainfall infiltrated into soil layer until it reaches a constant infiltration rate (fc) which is indicated an equilibrium subsurface flow rate. In hydrological view, time of concentration plays a significant role in elaboration of transformation of rainfall into runoff in a watershed. The aims of this research are to define influence of soil density and soil water content in determining time of concentration using infiltration concept based on water balance theory, and to find out the effect of land slope this time. Watershed laboratory experiment using rainfall simulator was employed to examine time of concentration associated with infiltration process under different slope, soil density and soil water content based on water balance concept. The steady rainfall intensity was simulated using sprinklers which produced 2 dm3∙min–1. Rainfall, runoff and infiltration analysis were carried out at laboratory experiment on soil media with varied of soil density (d) and soil water content (w), where variation of land slopes (s) were designed in three land slopes 2, 3 and 4%. The results show that relationship between soil density and land slope to time of concentra-tion showed a quadratic positive relationship where the higher the soil density address to the longer time of concentration. Moreover, time of concentration had an inverse relationship with soil water content and land slope that means time of con-centration decreased when the soil water content increased.

The paper is designed to present a method to estimate greenhouse gases (GHG) uptake or emissions in the absence of data for peat bog areas (GEST method). The paper presents the research results produced by a project on “Limiting CO2 emissions via the renaturalisation of peat bogs on the Eastern and Central European Plain”. The study area consisted of three peat bogs: Kluki, Ciemińskie Błota, and Wielkie Bagno (Słowiński National Park). The GEST method relies on the estimation of gas emissions on the basis of vegetation and water levels and greenhouse gas coefficients for each given habitat type provided in the research literature. The greenhouse gas balance was calculated for a baseline scenario assuming the lack of human impact and for a scenario taking into account human impact in the form of peat bog preservation. Initial research results indicate that there is a total of 41 GESTs in the studied bog areas and that a reduction in CO2 emissions of approximately 12% will occur following what is known as renaturalisation by raising the groundwater level, felling of trees across the bog, and making changes in habitats.