Well, it reaches from Kent and Essex in the east, to the borders of Wiltshire in the west, and as far as the South Downs. It includes the Chiltern and Cotswold hills. It's more than half the width of England, and I guess 100 miles north to south. I'm not sure that "pretty small" is fair.
I didn't know it stopped north of Luton, but I'm not surprised - I think three big rivers emerge at The Wash.
I think I guessed 30M for the population of the Thames watershed, based on 8M for London, maybe a dozen towns of more than 500,000 in the home counties, and loads of suburban sprawl and smaller towns. 30M is about 1/3 of the population of Britain, which seems about right. But even with a map of the watershed, it would be hard to estimate without a list of the populations of towns.
Perhaps I've overestimated the number of towns of over 500,000; I live in the largest conurbation in this county, and it's population is just 140,000.
Anyway, my point was that the watershed is big enough (and complex enough) that unless you happen to know the answer, estimating its population is pretty challenging.
I didn't know it stopped north of Luton, but I'm not surprised - I think three big rivers emerge at The Wash.
I think I guessed 30M for the population of the Thames watershed, based on 8M for London, maybe a dozen towns of more than 500,000 in the home counties, and loads of suburban sprawl and smaller towns. 30M is about 1/3 of the population of Britain, which seems about right. But even with a map of the watershed, it would be hard to estimate without a list of the populations of towns.
Perhaps I've overestimated the number of towns of over 500,000; I live in the largest conurbation in this county, and it's population is just 140,000.
Anyway, my point was that the watershed is big enough (and complex enough) that unless you happen to know the answer, estimating its population is pretty challenging.