This study presents measurements and modeled estimates of fall water requirements for the seasonal wetlands under moist soil management at Lower Klamath National Wildlife Refuge in northern California, USA. For three representative seasonal wetlands on the refuge, we measured the total volume of water required to fill the units and partitioned this volume into three components: surface water volume, ET losses, and soil-saturation requirements. Flood-up of seasonal wetlands required an average inflow rate of 0.87 ha-m/ha, with a range from 0.55 to 1.08 ha-m/ha. Over half of this water goes to saturate the underlying soils. We present a model for determining the approximate fall water requirement of any seasonal wetland on the refuge, given information on the effective porosity, depth to groundwater, average precipitation and ET, and the volumetric capacity of the wetland. Using a combination of measurements and modeled or assumed rates, we estimated the total fall water requirements for the refuge for 1999, 2000, and 2001. The estimates compared favorably with measured fall water deliveries to the refuge for the three years. Lastly, we compared annual water requirements for seasonally flooded and permanently flooded wetlands at Lower Klamath National Wildlife Refuge. Water requirements for the two wetland habitat types are approximately equal, although there are differences in the timing of demand and the consumptive use. Permanently flooded wetlands require water throughout the season to satisfy evapotranspiration needs, and none of this water is returned to the system. Seasonally flooded wetlands require water only in the fall during flood-up, and much of this water is returned to the system in the spring.