Seasonal Wetland. Wetland habitats on Xxxx and Pixley NWRs are grouped into three major categories: seasonally flooded xxxxx, moist soil impoundments, and summer water. These categories are addressed collectively as seasonal wetlands for this assessment. Seasonally flooded marshes are inundated fields or ponds that are managed primarily to grow seed and to produce invertebrates for migratory waterfowl, shorebirds, and other wetland-dependent wildlife. (Reclamation and CDFG, 1995). Primary food production plant species found within this habitat type on Xxxx and Pixley NWRs are watergrass (or wild millet) and swamp xxxxxxx. Water levels are managed to provide appropriate water depths for wintering waterfowl and shorebirds. At Xxxx and Pixley NWRs, seasonal xxxxx is flooded from October through February, although some units may be flooded as early as August or September if water is available to provide habitat for early arriving migratory waterfowl such as northern pintails. Optimal management of seasonally flooded xxxxx on the Xxxx NWR Complex requires approximately 2.5 to 3.4 acre-feet of water per acre (X. Xxxxx, 2000). Moist soil impoundments are similar to seasonal wetlands, except that they are irrigated in summer to improve production of watergrass and swamp xxxxxxx, the primary food producing species. Moist soil impoundments are typically irrigated during the summer to produce large quantities of these food plants. Water requirements differ among the plant species. Swamp xxxxxxx requires the least irrigation and, consequently, the least amount of water to produce. Watergrass can require several irrigations during the summer and has the highest water requirements of the moist soil plants (Reclamation and CDFG, 1995). Watergrass is considered to be one of the most productive and important waterfowl foods in California (Reclamation, et al., 1998) Production of food plants and management of seasonal wetlands typically has the following water management pattern (Reclamation and CDFG, 1995). Drawdown (draining of winter floodwater and drying of the soils) would occur in the spring. For swamp xxxxxxx, drawdown is usually accomplished in the last 2 weeks of March through the first 2 weeks of April. For units managed for watergrass, the drawdown is later, occurring from early April through early May. The soils dry and warm to allow germination of seeds and initial vegetation growth. Depending on weather patterns and soil composition, a first irrigation is applied during the las...
