SNOWMELT INFILTRATION USING HYDRUS-1D BASED ON A SNOW SURFACE ENERGY BALANCE MODEL FOR BUCEGI MOUNTAINS, ROMANIA.

An accurate simulation of snowmelt infiltration rates for an area of Bucegi Mountains, during spring thaw, has been made using the snow routine of HYDRUS- 1D. The model is based on coupled flow and heat transport in the vadose zone. The snowmelt routine is based on degree day concept. As boundary conditions are used, surface water and heat fluxes can be calculated from the energy balance equation. The variables of the surface energy balance equation and melt rates can be calculated using meteorological data: air temperature, precipitation, relative humidity, wind speed and cloud cover. For the inverse estimation of soil hydraulic properties given by van Genuchten-Mualem (vG-M) model, we used direct measurements of the soil water content. HYDRUS-1D code is based on the Levenberg-Marquardt (LM), a nonlinear minimization local algorithm with good results for homogenous soil. Multiple soil layers usually require the use of global optimization methods. We compare parameter estimation using LM local minimization algorithm and another promising method: ant colony optimization (ACO). ACO is based on the behavior of a colony of ants in order to find the shortest route between their nest and a food source. The climate change that impacts snowmelt infiltration rates in Bucegi Mountains were evaluated for Representative Concentration Pathway (RCP) 2.6 and 8.5 scenarios. The climate change scenario is considering that temperatures are rising, so the amount of snow and ice have diminished. This allows a deeper seepage of the water into the ground as well as the ground temperature increase. [ABSTRACT FROM AUTHOR]