Stable Isotope HydroCalculator
Algorithm
The calculations require the user to enter data in three steps, and results are then displayed in the fourth step.
Step 1: selection of the hydrological regime of the studied pool:
a) non-steady-state (no inflow to the pool, the water table decreases due to progressive evaporation) or
b) steady-state model (inflow equals evaporation).
Step 2: selection of the option for δA value determination:
1) the most accurate approach – it is required to known δA value based on field analyses;
2) δA calculated from stable isotope composition for precipitation (δRain) for the studied pool and season;
3) δA calculated from δRain and the slope of LEL. The selection in this step will determine what data need to be used in step 3.
Step 3: entering analysed stable isotope composition of water:
δP –initial value for water in the pool (for non-steady state) or value for water inflowing to the pool (for steady state)
δL – final value for water in the pool (for non-steady state) or a pool value (for steady state)
and measured parameters: T – temperature; h – relative humidity of air (as fraction); δA – the stable isotope composition of moisture in ambient air (if known); dRain –the stable isotope composition of precipitation (if δA is not known); LEL – if known for the study area.
Step 4: After entering all required variables, the calculated results will be displayed as a fraction of the evaporated volume f, or as fraction evaporation over inflow E/I, depending on the selected model. Along with results, the intermediate parameters, calculated based on entered variables, will be listed: kinetic isotope fractionation constant – Ck; kinetic isotope fractionation factor - εk; equilibrium isotope fractionation factor – ε*, total isotope fractionation - ε, fractionation factor - α, limiting isotopic composition – δ* and parameter m.
​
​
​
The full algorithm is avilable as a research paper (free access)
