ations shown in Figure A.2 of the GAWSER manual is fully programmed in Object-GAWSER. For
example, Figure A.2 shows that density is not calculated while the air temperature is above freezing.
But, in Object-GAWSER, density is calculated for above freezing temperatures.
To improve infiltration calculations in Object-GAWSER, the hourly value of TINF must be 94
estimated differently. For example, the difference in magnitude between peaks of F and GAWSER_F
in Figure 38 was improved by varying the initial value of TINF. Furthermore, an investigation of the
computational differences between Object-GAWSER and GAWSER should reveal better computa-
tional methods for calculating infiltration.
Major outputs, such as the liquid water released from the snowpack (LIQ_WTR_REL) and perco-
lation (P), are almost identical to their counterparts in GAWSER. Therefore, the discrepancies be-
tween snowpack density and infiltration estimates in Object-GAWSER and GAWSER (5.4) do not
detract from the overall accuracy of Object-GAWSER.
This version of Object-GAWSER has not been calibrated to any actual watershed and is therefore
only useful for instructive purposes and general estimates. A new, calibrated version that distributes
snowmelt among three different cover types is currently being developed by the author.
Object-GAWSER provides insight into watershed hydrology by enabling its users to visualize
hydrologic processes. With its animated objects, graphs and tables, users can observe the storage and
transport of water in watersheds. Furthermore, sensitivity analyses are easily performed within its
object-oriented environment. For example, users can change the value of any component of Object-
GAWSER and watch its outputs unfold over time with its graphs and tables. Therefore, the dynamic
simulation capabilities of Object-GAWSER show that it is a valuable tool for understanding hydro-
logic processes.
LITERATURE CITED
Chang, Chent-Nan, E.S. Da Motta and A.D. Koussis (1983) On the mathematics of storage routing.
Journal of Hydrology, 61: 357370.
Chard, H.P. (1983) A model of spatially-variable runoff from snowmelt and rain on agricultural
watershed. M.Sc. thesis (unpublished), School of Engineering, University of Guelph.
Dooge, J.C.I. (1973) Linear theory of hydrologic systems. U.S. Department of Agriculture, Agricul-
tural Research Service, Technical Bulletin 1408.
Ghate, S.R. and H.R. Whitely (1982) GAWSERA modified HYMO model incorporating areally-
variable infiltration. Transactions of the ASME, 25(1): 134142.
Haan, C.T., H.P. Johnson and D.L. Brakenseik (1982) Hydrologic modeling of small watersheds.
American Society of Agricultural Engineers, Monograph No. 5.
Holtan, H.N., G.J. Stilther, W.H. Henson and N.C. Lopenz (1975) USDAHL-74: Revised model of
watershed hydrology. Technical Bulletin 1518, Agricultural Research Service, U.S. Dept of Agricul-
ture.
McKim, H. L., E. A. Cassell and P.J. LaPotin (1993) Water resource modeling using remote sensing
and object-oriented simulation. Hydrological Processes, 7: 153165.
Mein, R.G., and C.L. Larson (1973) Modeling infiltration during a steady rain. Water Resources
Research, 9(2): 60-378.
Nash, J.E. (1959) A note on the Muskingum flood routing method. Journal of Geophysical Research,
64(8): 10531056.
Richmond, B. and S. Peterson (1994) STELLA II. Technical documentation. High Performance Sys-
tems, Hanover, New Hampshire.
Schroeter, H. (1988) An operational snow accumulationablation model for area distribution of shal-
low ephemeral snowpacks. Ph.D. Thesis (unpublished). School of Engineering, University of Guelph.
Schroeter, H. (1989). GAWSER Training Guide and Reference Manual. School of Engineering, Uni-
versity of Guelph, Ontario, Canada.
53
Previous Page
