Don’t venture on to the South Platte River in Littleton this weekend — or risk getting a citation if you do. With a drought-stricken flow approximately 20 times weaker than normal, the river is in no condition to be an aquatic playground. Littleton, fearing damage to the Platte’s river bottom from hundreds of people trudging through an anemic flow, is banning all activity in its stretch of the waterway — from C-470 to East Belleview Avenue. The ban starts at midnight Saturday and lasts through 6 a.m.