Keep Up Meaning

(intransitive, idiomatic) To stay even or ahead.

Example: 1992, The Daily Telegraph, London
  The NRA is pumping groundwater into the River Itchen in Hampshire to keep up its flow and is trying to save three streams, the Tong, the Little Stour and the Dour from going dry this summer.
1991, Tennis World, Sussex: Presswatch
  Keep up the good work of entertaining your fans on court Steffi; we know you can do it; your fans are behind you all the way.
1991, Barty-King, Hugh, The worst poverty, Gloucester: Alan Sutton Publishing Ltd, pages 85-203
  If the borrower could no longer afford to keep up the payments, the longer he stayed in the home the more the interest bill mounted.
  They ran so fast I could hardly keep up.
2012 May 13, Alistair Magowan, “Sunderland 0-1 Man Utd”[1], BBC Sport:
  Rooney and his team-mates started ponderously, as if sensing the enormity of the occasion, but once Scholes began to link with Ryan Giggs in the middle of the park, the visitors increased the tempo with Sunderland struggling to keep up.
To ensure that one remains well-informed about something
  I always try to keep up with (or "keep up on") current affairs.