Markvattenbalans

Markvattenbalans is a hydrological concept that describes the balance of water stored in the soil within a given soil layer, typically the root zone, over time. It accounts for all sources and sinks of soil water and is used to assess how much water is available for plants, how much may recharge deeper groundwater, and how soil moisture responds to weather and land use.

Key components include inputs such as precipitation and infiltration of water from above, and outputs such as evapotranspiration by vegetation, drainage to deeper soil or groundwater, and surface runoff. The change in soil water storage equals inputs minus outputs. The values depend on soil properties (texture, structure, porosity), rooting depth, land cover, and climate. In practice, models may separate root-zone storage from deep drainage, and may compare potential evapotranspiration with actual evapotranspiration to estimate soil moisture deficits.

Measurement and methods involve direct soil moisture sensing, lysimeters, and gravimetric methods, as well as modelling approaches ranging from simple bucket models to more comprehensive soil-vegetation-atmosphere transfer frameworks. Remote sensing can provide large-scale estimates of soil moisture, complemented by meteorological data for model inputs.

Applications include irrigation planning and scheduling, drought monitoring, water resources management, and climate impact assessment. Limitations of markvattenbalans analyses arise from spatial and temporal variability in soils, uncertainties in infiltration and deep drainage, groundwater interactions, and the rapid changes in moisture following rainfall events.