Dr. Nicolas Zegre

Measuring & predicting streamflow

Runoff and Streamflow

•Streamflow: water flowing in streams•measured in volume per time: discharge (Q)

cubic feet per second (cfs), liters per minute (lpm), cubic meters per minute, gallons per day…

•Runoff: volume of water in the stream expressed as a depth per time• not depth of water in stream! • depth of water if it was spread back over the watershed• Q divided by watershed area

vAort

LQ

3

t

L

LtL

A

Qro

2

3

orange

Pygmy

Flow Tracker

)()/( 2LareaxtLvelocityQ

Measuring Q

Rating curve development• rating curve – relationship between

stage and Q

One-to-One regression model: Predicting Q f(P)

Predicting in ungaged basins

Ground-based climate station (NOAA)

Streamflow station (USGS)

Benefits:• Climate robust predictor of Q• Quantify error & uncertainty

Drawback:• Few stations where you need

them!• De-synchronization

Regionalization: Predicting Q f(climate, terrain, landcover)

Predicting in ungaged basins

Ground-based climate station (NOAA)

Streamflow station (USGS)

1. Catchment dimensions (area, perimeter)

2. Shape (elongation)3. Topography (slope, aspect)4. Stream network (drainage density,

stream gradient)5. Geology and soils6. Vegetation (LAI, species)7. Climate (gridded datasets vs.

timeseries)8. Landuse9. Response metrics:

1. Mean overland flow distance2. Mean flow distance to streams3. Mean solar radiation index4. Mean topographic wetness

index

Regionalization: Predicting Q f(climate, terrain, landcover)

Predicting in ungaged basins

Benefits:• Few stations where you need them!• Uses available spatial data• Can be a robust predictor of Q

Drawback:• Not always a robust predictor of Q• Requires network of regional stream &

climate stations