Both parks are very flat, and the sections nearer the river are seasonally flooded. The resulting watery grassland reflects the sky like a mirror, for as far as you can see. It is quite a sight, and a remarkable environment for both animals and waterfowl.
In both parks you'll find a variety of quite clearly defined environments, as you move away from the waterways to the dry, permanent woodlands. Immediately beside the water, you'll find very large areas of open grassland which are seasonally flooded – a classic floodplain environment. On the drier side of this, where the grassland does not receive a regular annual flooding, termitaria can exist – with high solid mounds (often looking like chimneys) to keep their occupants safe from drowning in the occasional exceptional flood. This is a very distinct area in the grasslands, known as the termitaria zone.
Further away still, where there's absolutely no risk of flooding, you'll find a variety of trees in the woodlands which extend across the south of Lochinvar and the north of Blue Lagoon.
Kafue River Floods
The Kafue River was dammed in two stages. Firstly, in 1971 a dam was built in the Kafue Gorge, just south of Lusaka, which permanently flooded 800–1,100km2 of land on the eastern side of the Kafue Flats. However, the gradient of the river above this point had always been very low (about 8m drop in over 200km of river!) – thus the result was a huge, shallow reservoir with a relatively low volume (785 million cubic metres). The Kafue dam's primary purpose was to provide hydro-electric power: it supplies up to 75% of Zambia's electricity. To guarantee this it needed a reservoir which was effectively larger than this.
Thus a second dam was built and closed in 1977: the Itezhi-Tezhi dam. This is about 450km upstream of the Kafue dam, and flooded only 300km2 of land with a much deeper lake – holding about 4,925 million cubic metres of water. Hence the flow from Itezhi-Tezhi could be regulated to provide the constant flow needed by the Kafue dam to generate electricity. When constructed, ZESCO (Zambia Electricity Supply Corporation) was obliged to ensure that there was a continuous flow out of Itezhi-Tezhi, in order to preserve the Kafue Flats habitat, and service the other users of the water. (The largest of these are the sugar industry around Mazabuka, and the municipality of Lusaka, which extracts water for the city.) However, this was a very difficult task – made all the more complex because the flood takes about six weeks to get from Itezhi-Tezhi to the Kafue dam.
Before the dams, the river's flow varied enormously with the season: the Kafue Flats flooded every year and the floodplains experienced a long dry season. Since the dams, ZESCO have released a four-week artificial 'flood' in March, but clearly it has failed to simulate the natural situation. The UK's Department for International Development (DFID) reported in 2001 on Managed Flood Releases from the Itezhi-Tezhi Reservoir, and within that noted:
Since the dams, the flooding pattern has changed considerably. There has been a reduction in the seasonal fluctuations… The annual minimum flood area has increased from about 300km2 to approximately 1,500km2. In places permanent lagoons have formed in places where ephemeral aquatic habits had existed before… In broad terms, the western half of the Flats is drier, whilst the eastern half is wetter than they were prior to dam construction.
This altered flood pattern has knock-on effects to the whole ecosystem. Old-time visitors to Lochinvar will tell you that the vegetation there has changed enormously over the last 30 years, and not for the better. With the change in vegetation, come changes in the grazing – for both wildlife and cattle. Then, of course, the breeding cycles of the fish are affected and there's no longer any movement of fish up-river past the dams. When fish populations change, so do those of many bird species.
There is much further research to be done, and the WWF are already involved in a project to simulate the river's old flood regime using new computer models to control the Itezi-Tezhi dam outflow. Many people are now starting to make strenuous efforts to ensure that whilst maximising the benefits provided by these dams, they also minimise the inevitable environmental problems caused by them.