real function dstg
     i         (ai,k7,
     m          rn1)
c
c     + + + PURPOSE + + +
c     Provides numbers from a gamma distribution, given two random numbers.
c
c     + + + ARGUMENT DECLARATIONS + + +
      real ai,rn1
      integer k7(4)
c
c     + + + ARGUMENT DEFINITIONS + + +
c     ai          -
c     k7          - Seed for random number generation.
c     rn1         - ??? -- used for precip gamma dsn
c
      include 'crandom.inc'
c
c     + + + FUNCTION DECLARATIONS + + +
      real randn
c
c     + + + LOCAL VARIABLES + + +
      real xn1, rn

c     + + + DATA INITIALIZATIONS + + +
c     data xn1/10.0/
c
c     Modified by Bofu Yu on July 4, 1999
c                        based on break-point data, B.YU
      data xn1/6.28/
c
c     + + + END SPECIFICATIONS + + +
c
c -- XXX -- Changed 1/5/2000 -- CRM:
c     double precision xx
      double precision fu,xx
 10   dstg=rn1
        xx=rn1*ai
        rn=randn(k7)
        fu=xx**xn1*exp(xn1*(1.0-xx))
        rn1=rn
      if (fu.lt.rn) goto 10
c
      return
      end