Lysimetry

Lysimetry is the measurement of water movement in soils and plant systems through the use of lysimeters. A lysimeter is a device that isolates a known soil volume so that changes in water storage, drainage, and evapotranspiration can be quantified directly. The technique supports a water-balance approach to determine how precipitation, irrigation, and other inputs are partitioned among ET, drainage, and storage changes.

Principles and methods: In a field lysimeter, boundary conditions are controlled to minimize lateral water fluxes. Precipitation and irrigation are recorded or controlled, while drainage leaving the lysimeter is collected and weighed or measured. Soil water storage is monitored with sensors or by measuring weight changes. ET is typically inferred from the water balance: ET ≈ P + I − D − ΔS, where P is precipitation, I is irrigation, D is drainage below the lysimeter, and ΔS is the change in soil water storage. Weighing lysimeters use load cells to detect minute weight changes, translating them into water losses. Other approaches track volumetric water content or extract pore water for analysis.

Types: Lysimeters vary by design and boundary conditions. Monolithic or intact soil lysimeters use undisturbed soil cores, while drainable or weighing lysimeters separate drainage collection from the soil body. Some configurations emphasize direct ET measurement, others focus on leachate chemistry to study nutrient or contaminant transport.

Applications and limitations: Lysimetry is employed in agriculture, hydrology, and environmental science to assess crop water use, evaluate irrigation strategies, quantify deep drainage, or study nutrient leaching. Limitations include high cost, small representative area, potential root disturbance, boundary effects, and the need for careful calibration. Despite these challenges, lysimeters provide direct, process-based data that complement model-based evapotranspiration estimates.