SUBROUTINE RANDM(X, A, MRND, RNUMB)
C
C     + + + PURPOSE + + +
C
C     RANDM COMPUTES RANDOM NUMBERS BY A MULTIPLICATIVE CONGRUENTIAL
C     METHOD:
C
C     X = A*X MOD M,  RNUMB=X/M
C
C     NOTE: BGNRND SHOULD BE USED TO INITIALIZE X (THE CHECKS MADE 
C     THERE [A*M AND A CAN BE REPRESENTED EXACTLY IN X AND U] ENSURE 
C     THAT SUCESSIVE VALUES OF X CAN BE CALCULATED EXACTLY)
C
C     THE NUMBER OF SIGNIFICANT DIGITS IN THE RESULT IS ROUGHLY THE 
C     MINIMUM OF:
C     1) THE NUMBER OF SIGNIFICANT DIGITS IN RND, AND
C     2) THE NUMBER OF SIGNIFICANT DIGITS IN U LESS THE NUMBER OF
C        DIGITS OF THE MULTIPLIER IN A
C
C     WHEN U IS DOUBLE PRECISION, ALL THE DIGITS IN RND ARE
C     SIGNIFICANT
C
C     INITIALIZES PARAMETER VALUES FOR HYDROLOGY COMPONENT.
C
C     CALLED FROM PSIINV
C     AUTHOR(S): D. FLANAGAN, J. ASCOUGH
C     VERSION: THIS MODULE TAKEN FROM ASCOUGH STANDALONE IRS CODE
C     DATE CODED:  3-24-2005
C     CODED BY: D. FLANAGAN
C
C
C     + + + ARGUMENT DECLARATIONS + + +

      REAL X, A, MRND, RNUMB
     
C     + + + ARGUMENT DEFINITIONS + + +
C
C     X       -
C     A       -
C     MRND    -
C     RNUMB   - RANDOM NUMBER RETURNED FROM SUBROUTINE
C     
C     + + + LOCAL DECLARATIONS + + +
      REAL V
      DOUBLE PRECISION U

C     + + + LOCAL DEFINITIONS + + +
C     V       - HOLDS INTERMEDIATE RESULTS
C     U       - HOLDS INTERMEDIATE RESULTS

C     + + + END SPECIFICATIONS + + +

      X = A * X
      U = X / MRND
      V = U
      V = AINT(V)
      X = X - V * MRND
C
      IF (X.LT.0.D0) THEN
         V = V - 1.
         X = X + MRND
      END IF
C
      RNUMB = U - V
C
      RETURN
      END