Microbes form colonies to pool resources and better cope with changes in environmental conditions including nutrient availability and hydration status. The excretion of extracellular polymeric substances (EPS) plays an important role in forming colony structure, anchoring to solid surfaces, nutrient entrapment and many other functions. In this study we focus on the micro-hydrological functions of EPS enabling microbial activity in the presence of large spatial and temporal variations in hydration status common to the shallow vadoze zone. We will review key hydraulic and transport properties and postulate mechanisms conferring advantage to microbial colonies embedded in EPS. Relationships between pore space geometry, physical constraints and, EPS production and morphology will be studied. The morphology of EPS and, its effect on the internal arrangement of microbial colonies (typical sizes) will be evaluated under diffusion constraints imposed by conditions in unsaturated soil pores.