Catchment area-weighted rainfall
User-supplied measurements and assumptions; Influence-area weighted rainfall; one mm over one km² equals 1000 m³.
Hydrology and water resources ↗Hydrology and water resources calculators
25 calculators. Search or choose one below.
Calculators
Rainfall double-mass selected-split slopes
User-supplied measurements and assumptions; Compare through-increment mass slopes before and after a user-selected split; this diagnostic does not establish a causal station change.
Hydrology and water resources ↗Rainfall missing-gauge estimate
User-supplied measurements and assumptions; Normal-ratio estimate: average of neighbor observed precipitation × target normal/neighbor normal.
Hydrology and water resources ↗Rainfall timestamp-gap event grouping
User-supplied measurements and assumptions; Positive-rain timestamps at least supplied gap apart begin a new event; timestamps represent observed impulses, not unmeasured rainfall intervals.
Hydrology and water resources ↗Hyetograph time-block aggregation
User-supplied measurements and assumptions; Bin timestamp-assigned rainfall into half-open fixed blocks starting at zero; boundary samples enter the next block.
Hydrology and water resources ↗Storm moving-window maxima
User-supplied measurements and assumptions; Exhaustive moving-window sums over complete intervals; no fractional interval interpolation.
Hydrology and water resources ↗Rational peak-flow worksheet
User-supplied measurements and assumptions; Rational Q=C×i(mm/hour)×A(hectares)/360; constant intensity and representative time of concentration assumed.
Hydrology and water resources ↗Kirpich channel travel time
User-supplied measurements and assumptions; SI Kirpich channel component tc=0.0195L^0.77S^-0.385; empirical calibration, not all-catchment universal validity.
Hydrology and water resources ↗Curve-number runoff scenario
User-supplied measurements and assumptions; Curve-number event model S=25400/CN−254 mm, Ia=λS, Q=(P−Ia)²/(P−Ia+S) above Ia.
Hydrology and water resources ↗Infiltration Horton fit
User-supplied measurements and assumptions; Bounded variable-projection least squares for Horton f(t)=fc+(f0−fc)e^(−kt); reject nonphysical fitted rates.
Hydrology and water resources ↗Ponded Green-Ampt infiltration
User-supplied measurements and assumptions; Ponded Green-Ampt implicit equation ΔF−ψΔθ ln((F+ψΔθ)/(F0+ψΔθ))=KΔt; no finite rainfall-supply restriction.
Hydrology and water resources ↗Unit hydrograph convolution
User-supplied measurements and assumptions; Discrete convolution with unit hydrograph expressed per 1 mm excess rainfall and matching rainfall-block duration.
Hydrology and water resources ↗Hydrograph baseflow separation
User-supplied measurements and assumptions; Straight line between supplied endpoint baseflows, clipped to measured flow so direct runoff remains nonnegative.
Hydrology and water resources ↗Hydrograph volume integration
User-supplied measurements and assumptions; Trapezoidal integration of discharge over strictly increasing timestamps; linear variation between observations.
Hydrology and water resources ↗Reservoir level-volume interpolation
User-supplied measurements and assumptions; Piecewise-linear storage interpolation inside the surveyed stage range; out-of-range queries rejected.
Hydrology and water resources ↗Reservoir implicit continuity routing
User-supplied measurements and assumptions; Implicit-Euler level-pool continuity Snext+Δt Qout(hnext)=Sprevious+Δt Qin; invert monotone supplied storage/outlet curves, reject storage overflow.
Hydrology and water resources ↗Flood routing Muskingum worksheet
User-supplied measurements and assumptions; Classical linear Muskingum recurrence; require nonnegative coefficients (2KX≤Δt≤2K(1−X)).
Hydrology and water resources ↗Channel flow gauging sections
User-supplied measurements and assumptions; Velocity-area subsection method; signed velocities allow measured local reverse flow.
Hydrology and water resources ↗Stage-discharge supplied-offset power fit
User-supplied measurements and assumptions; Power rating Q=A(h−h0)^b via log-space least squares with user-supplied h0; no automatic datum fitting.
Hydrology and water resources ↗River flow-duration curve
User-supplied measurements and assumptions; Sort valid observations descending and use Weibull exceedance rank m/(n+1); missing days must be removed explicitly.
Hydrology and water resources ↗Drought single-period rolling minimum
User-supplied measurements and assumptions; Complete consecutive-day rolling means over one supplied analysis period; gaps and cross-year grouping are not inferred.
Hydrology and water resources ↗Groundwater Darcy flux
User-supplied measurements and assumptions; Darcy magnitude q=K×hydraulic gradient, Q=q×area; homogeneous saturated steady flow.
Hydrology and water resources ↗Groundwater seepage velocity
User-supplied measurements and assumptions; Mean advective pore velocity=q/effective porosity; travel time=distance/velocity.
Hydrology and water resources ↗Groundwater Cooper-Jacob drawdown fit
User-supplied measurements and assumptions; Cooper-Jacob late-time confined-aquifer straight-line approximation; user selects valid data window, T=2.303Q/(4πslope), S=2.25Tt0/r².
Hydrology and water resources ↗Water allocation deficit ledger
User-supplied measurements and assumptions; Add inflow, deduct supplied losses, satisfy high then lower priority from available storage; no capacity spill or legal allocation rules.
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