Regionalisation

Question 1

Meaning

Answer 1

Transferring of low flow statistics from observed to ungauges sites

Question 2

1) Scaling with drainage area ratio:

Answer 2

NMQa/NMQb = Areaa/Areab

Question 3

2) Multiple regression:

Answer 3

 Regression can be applied on low flow statistics directly or on moments/ L-moments of distributions for low flow statistics

 Regression applied separately for homogeneous regions might improve performance (Nathan & McMahon, 1990)

 Relevant predictors: temperature characteristics, precipitation characteristics (mean annual, dry spell durations, etc.), evaporation, standardized precipitation index (SPI), etc.

Note: Standardized Precipitation Index (SPI): standardized deviation of accumulated precipitation sums over n months from the long term normal applying a standard normal distribution N(0,1) to the precipitation data after transformation

Question 4

3) Geostatistical approaches

Answer 4

Geostatistical approaches take into account the spatial persistence of low flow statistics for interpolation (see course “Geostatistics”)

Some Methods:
 Ordinary kriging (OK)
 External drift kriging (EDK)
 Topological kriging (TK)