Freshwater discharge into the Gulf of Alaska (GOA) has an important effect on coastal circulation. In order to incorporate freshwater discharge into a three-dimensional ocean circulation model with both point sources (big rivers) and line sources (gridded coastlines) a digital elevation model (DEM) was developed to simulate freshwater discharge into the GOA under forcing of daily air temperature and precipitation data from National Centers for Environmental Predication/National Center for Atmospheric Research reanalysis during 1958--1998. This GOA-DEM includes glacier, snow storage, and melting processes. Coastal freshwater discharge into the GOA displays a very strong seasonal cycle and interannual variability. The comparison of simulated runoff with gauged (observed) river discharge was conducted for two major rivers (Copper River and Susitna River), showing a good agreement on seasonal cycle and interannual variability. The simulated annual mean of the total freshwater discharge into the GOA ranges from 19,000 to 31,000 m3 s-1 (with a mean of 23,100 m3 s-1) for the period 1958--1998. In the winter season (November to April), precipitation is mainly stored as snow, and freshwater discharge remains as a small base flow with some occasional changes due to short-term temperature increase. Freshwater discharge starts to rise sharply from May because of increasing precipitation and above-freezing temperatures and remains high from June through September because of snowmelt and some melting glaciers. In October the discharge decreases rapidly, to a basic flow in December as the temperature drops below the freezing point. Freshwater discharge into the GOA can be divided into the point sources (big rivers) and the line sources (ungauged numerous small streams and creeks due to melting of snow and glaciers). The model shows that five major rivers (point sources) account for about 50.6% of the total drainage areas, while the line source accounts for 49.4% of the drainage area. However, our new finding is that the point sources only account for 26%, while the line sources contribute 74% to the total runoff. Thus discharge from line sources (ungauged small rivers, streams, and creeks) is 2.8 times greater than from the point sources (five large rivers).