"El Brujo" Waterfall in Reserva El Chocoyo, Ticuantepe
Yes, there are lakes and waterfalls in and near Managua, Nicaragua. Lake Managua is the northern edge of the city of Managua. The nicest part of this is that there has been a lot of investment in the area called Puerto Salvador Allende. This area has a nice boardwalk, restaurants, snack shacks, parks, and traditional handicrafts. Also at the port, there is a cruise boat that takes tours around the lake. In particular, the evening outing is nice because as the sun sets you can see the lights of Managua turn on, creating a magical visual effect.
As for waterfalls, yes, there are waterfalls just outside of Managua in an area called Chocoyero-El Brujo in Ticuantepe. This is a private forest reserve that includes great hiking areas with the big payoff of seeing a wonderful cascade of water that keeps the area very fresh and full of wildlife, mostly birds including parrots. The odd thing about this area is that when the Spaniards arrived and the indigenous peoples told them about the waterfall, they did not believe them as no river runs in the area. Well, the ground is so porous due to its volcanic nature, that the water from the fall just goes a few feet before sinking into the lava rock!
I hope you enjoyed learning a little about the water features of Managua, Nicaragua.