Hydrometeorological aspects of problems of soil and vegetation in urbanized river systems
02 / 2002 - 02 / 2005
In urbanized river systems, many interactions occur between hydrometeorological processes and conditions of soil and vegetation. Percipation may infiltrate covered or bare soil surfaces, may be intercepted by above-ground parts of vegetation, may be stored in the tree root zone, may leak to deeper soil layers that are out of reach of tree roots, and/or may runn off from covered or bare surfaces. Transpiration of vegetation involves large amounts of water. The transpiration and evaporation influence air temperture and humidity. Vegetation like trees provides shadow and shelter. The involved mechanisms and the impacts of their effects greatly depend on the condition of the vegetation. The condition of urban vegetation is often very suboptimal. This is often caused by water deficts. Such deficts may be due to a too low soil water holding capacity, a restricted root zone, a limited infiltration capacity of soil and cover, the occurrence of run-off, etc. Urban governments aim at the improvement of suboptimal conditions of vegetation. This tendency will change the interaction between hydrometeorological processes and conditions of soil and vegetation on many places in the near future. The project aims at quantifying water deficts and analyzing the involved water regimes/balances. A range of tree growing sites will be selected in an urbanized river system, with different depths of groundwater table. Water balance of tree growing sites with shallow groundwater depths may include water supply by capillary rise from the groundwater. Sites where the boundaries of the tree root zone can be identified have preference. For each experimental site, data on potential transpiration will be collected and/or derived. Tree condition will be assessed for each site. Assessment will use visual as well as quantitative methods. It will be attempted to estimate water deficts from potential transpiration and tree condition. Water deficts will be analyzed by analyzing the water balances. This includes collection of precipation data, estimations of interception by above-ground vegetation parts, evaporation from the surface and runn-off, capillary rise from groundwater, water infiltration through covered of bare surfaces, water lekage losses, water storage capacity of the root rone, water use by vegetation. The project will contribute to a better understanding of the hydrometeorological changes that accompany human activities aiming at improving tree conditions.