Hydrology
Hydrology calculators for watershed area, rational method, curve number, flood frequency, evapotranspiration, and dam spillway.
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Dam Spillway Design
Calculate spillway discharge capacity using the weir equation. Determine flow rate, approach velocity, and energy dissipation for dam spillway design.
Evapotranspiration Calculator
Estimate reference evapotranspiration (ET₀) using a simplified Penman-Monteith approach from temperature, humidity, wind speed, and solar radiation.
Flood Frequency Analysis
Estimate the design flood discharge for a given return period using a simplified log-Pearson Type III frequency analysis.
Groundwater Recharge
Estimate annual groundwater recharge from precipitation, runoff coefficient, and evapotranspiration using the water balance method.
Rational Method Runoff
Calculate peak stormwater discharge using the Rational Method (Q = CIA/360). Estimate runoff from rainfall intensity, runoff coefficient, and catchment area.
SCS Curve Number
Calculate runoff depth using the USDA SCS (NRCS) Curve Number method. Determine runoff, infiltration, and initial abstraction from precipitation and curve number.
Stream Flow Calculator
Calculate stream discharge from average velocity, channel width, and depth. Includes Froude number, hydraulic radius, and flow regime classification.
Unit Hydrograph Calculator
Calculate the SCS triangular unit hydrograph peak flow, time to peak, and time base from drainage area, lag time, and storm duration.
Water Budget Calculator
Calculate the water balance for a watershed or region. Determine storage change from precipitation, evapotranspiration, runoff, and groundwater outflow.
Watershed Area Calculator
Calculate drainage area and morphometric parameters of a watershed from perimeter, shape factor, and longest flow path.