"The Nile" kind of grows on you.

At first, Jacques and Philippe Cousteau's two-hour special, airing tomorrow and Monday nights at 8 on Channel 26, seems to be just another travelogue.

We get the elephants and hippopotami, the lions at play, the giraffes galloping in panic from the plane's shadow, and the flamingo and zebras and gorgeous shots of the veldt, and even those cute animal scenes (pelicans diving in unsion; a pilot bird being swamped when his hippo dives) that I thought we had outgrown. Disney lives!

And the narration by Theodore Strauss: There must be a school of travelogue talk somewhere. We meet the Dinka, "a healthy, cheerful people, . . . fiercely independent." We are told that the Abu Simbel monuments are "mute testaments of past glory," and that "much of Africa long lay shrouded from Western eyes."

But in the end it is worth the two hours. For what starts as a strictly conventional nature piece winds up as a fascinating study of what happens when engineers start fooling around with infinitely complex ecosystems.

The Aswan High Dam has transformed Egypt in 11 years, as everyone knows, turning the desert green for miles, bringing abundant electric power, controlling the annual floods.

But as the Cousteaus take us steadily down the 4,000-mile river, we see some other effects. The ancient treasures at Abu Simbel and Philae were saved from the lake that backed 300 miles upriver from Aswan, but thousands of villagers weren't so lucky. The entire city of Wadi Halfa and its, 52,000 people were displaced.

Salt that normally washed away with the annual floods now remains on the soil, threatening to ruin it. The tons of slit that used to flow onto the lowlands as free natural fertilizer no longer arrive, which means that much of the new electricity has to be used to make and transport bagged fertilizer to the farmers.

And because the slit doesn't reach the delta, the Mediterranean is starting to invade the rich land at shoreside, like Holland in reverse.

Canals are dug; they get clogged with water hyacinths; deadly 2-4-D defoliant is sprayed on them, to what eventual effect no one quite knows. A giant 200-mile canal is being run through the Sudan -- without arrangements for people and animals to cross it. These things are laid out before us by the Cousteaus so casually that it seems almost accidental. But it isn't.

Along the way they show us incredible stormclouds of flies, a metropolis of bats, a young villager intrepidly allowing himself to be fitted with a snorkel so that beneath the muddy surface he can see the fish that are his livlihood.

Readers of Alan Moorehead's books on the Nile will be dissappointed with the cursory and not very accurate bits of history here. And we could have used a map. But in the end we discover that we have taken on a huge amount of information almost before we knew it.

The film is in memory of Philippe Cousteau, who was killed at 39 this summer after finishing the Nile project.