Water Balance Surplus Deficit Classifier

Conserve sequential single-bucket soil water with precipitation, PET, actual evaporation, overflow surplus and unmet-demand deficit; no groundwater recharge/irrigation guarantee and all bucket processes are declared simplifications.

Description

A soil-water bucket is a simplified monthly water balance.

A soil-water bucket is a simplified monthly water balance. Rain fills the available store, potential evapotranspiration sets atmospheric demand, and a fixed capacity separates retained water from surplus; unmet demand becomes a deficit.^[1]

When to use Water Balance Surplus Deficit Classifier

Use this tool to conserve sequential single-bucket soil water with precipitation, PET, actual evaporation, overflow surplus and unmet-demand deficit; no groundwater recharge/irrigation guarantee and all bucket processes are declared simplifications.

Prepare the climate observations and any independently chosen thresholds or model parameters. Confirm units, daily coverage, time order and the intended seasonal window.

How to use Water Balance Surplus Deficit Classifier and understand its results

Prepare the climate observations and any independently chosen thresholds or model parameters. Confirm units, daily coverage, time order and the intended seasonal window.
Enter intervalPrecipitationMm, intervalPotentialEtMm, soilBucketCapacityMm, initialBucketStorageMm using the field table and calculation rules, then run the tool.
Read intervalActualEtMm, intervalSurplusesMm, intervalDeficitsMm, intervalEndStorageMm. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
intervalPrecipitationMm	Interval precipitation mm	list of number	Required
intervalPotentialEtMm	Interval potential et mm	list of number	Required
soilBucketCapacityMm	Soil bucket capacity mm	number	Required
initialBucketStorageMm	Initial bucket storage mm	number	Required

Enter aligned nonempty precipitation and potential evapotranspiration lists in mm, a nonnegative capacity and initial storage between zero and that capacity. For each period in order, the calculation supplies evapotranspiration from initial storage plus precipitation, caps remaining storage at capacity, and records surplus and unmet demand. It returns a value for every input period in each result list.

Paired lists must be nonempty and have equal lengths.

available = storage_previous + rain; actual ET = min(available, PET); storage = min(available − actual ET, capacity); surplus = max(0, available − actual ET − storage); deficit = PET − actual ET

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
intervalActualEtMm	Interval actual et mm	list of number
intervalSurplusesMm	Interval surpluses mm	list of number
intervalDeficitsMm	Interval deficits mm	list of number
intervalEndStorageMm	Interval end storage mm	list of number

json

{
  "input": {
    "intervalPrecipitationMm": [
      5,
      20
    ],
    "intervalPotentialEtMm": [
      10,
      10
    ],
    "soilBucketCapacityMm": 10,
    "initialBucketStorageMm": 5
  },
  "output": {
    "intervalActualEtMm": [
      10,
      10
    ],
    "intervalSurplusesMm": [
      0,
      0
    ],
    "intervalDeficitsMm": [
      0,
      0
    ],
    "intervalEndStorageMm": [
      0,
      10
    ]
  }
}

Limitations and assumptions

This single bucket has no runoff timing, infiltration limits, groundwater flow, snow accumulation or plant-specific extraction curve. Precipitation becomes available before demand is applied within each period. Use consistent periods and an independently justified storage capacity.

Numeric inputs and returned numeric values must be finite; an unrepresentable returned value produces an error. Numeric lists are limited to 100,000 entries; the rules above may require smaller limits. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use Thornthwaite PET Monthly: Evaluate basic monthly Thornthwaite PET from twelve temperature/daylight/month-length normals with explicit heat index and high-temperature calibration-domain refusal; no measured ET or soil budget. For a complementary task, use Thornthwaite Moisture Index: Calculate named Thornthwaite Ih-0.6 Ia from caller precomputed monthly soil-water surplus/deficit and PET; not precipitation-minus-PET substituted for a full soil water budget.

References

Water Balance Surplus Deficit Classifier — tool.io

Similar or alternative tools

Thornthwaite PET Monthly
Evaluate basic monthly Thornthwaite PET from twelve temperature/daylight/month-length normals with explicit heat index and high-temperature calibration-domain refusal; no measured ET or soil budget.
Thornthwaite Moisture Index
Calculate named Thornthwaite Ih-0.6 Ia from caller precomputed monthly soil-water surplus/deficit and PET; not precipitation-minus-PET substituted for a full soil water budget.