The lack of data may render any estimate to nothing better than a guess.
That said, perhaps Parrault's method would serve your needs.

Pierre Parrault (1608-1680) estimated that 1/6 of the rainfall appeared as
stream flow. The method by which Parrault calculated the runoff was simple
and generally correct theoretically. Parrault first estimated the rainfall
in the Seine River watershed above Paris on an annualized basis. He then
estimated the river flow volume for the same period. By dividing rainfall
by stream flow, Parrault concluded that 1/6 of the rainfall equaled the
stream flow volume.

Steven R. Potter
Blackland Research Center--TAES
Temple, TX

254-774-6111
spotter@...



-----Original Message-----
From: hydrologymodel@...
[mailto:hydrologymodel@...]
Sent: Wednesday, November 08, 2006 5:49 AM
To: hydrologymodel@...
Subject: [hydrologymodel] Digest Number 260

Date: Wed Nov 8, 2006 11:05 am
From: "Nandakumar" pnkm62@...
Subject: Runoff estimation in ungauged catchment


Hi
I am currently crrying out water management studies in a hard rock
watershed (1000 sq.km) in Tamil Nadu and needs to compute the non-
committed surplus runoff available for my studies. As there are no
gauging stations, I have to use empirical methods for runoff
computation. I've computed the monsoon rainfall for the raingauge
stations using Theissen Polygon method and was planning to use
Strang's tables for runoff estimation. However, one of my polygons
have normal rainfall > 1000 mm. (hilly area, mostly) and I find that
Strang's Tables are available only upt 600 mm rainfall. Can anybody
tell me whether it is proper to extrapolate the curves graphically
using the available data ? If not, what other methods could I use?
Curve Number method is out of question as I don't have enough data
for that!

Recently I came across a software namely 'WADI' by ENEX Corporation,
which has a subroutine for runoff estimation. However, I am not able
to find any information or user manual of the program ( for the
theoritical background of the equations used etc.)anywhere. Any
suggestions.

Thanking you in advance

regards

Nandakumar