that growth and seed production of annuals were enhanced when soils were saturated or flooded 

 to approximately one-third the height of the recently germinated annuals (Chabreck 1960; Kadlec 

 and Wentz 1974; Fredrickson and Taylor 1982). With cooperative weather, many ponds were 

 completely filled with dense growths of Walter's millet, bearded sprangletop, and flatsedges. 

 Despite being short lived, annual vegetation was quite often so thick that it obscured the ponds 

 and interfered with waterfowl use and hunting. Virtually all traces of annual vegetation were gone 

 by the following year. In its place, desirable submerged aquatic plants such as sago pondweed, 

 southern naiad, and widgeon grass often filled the water column throughout the pond. Over 

 several years, the density of aquatic plants would gradually taper off, and through plant succession, 

 undesirable aquatics such as coontail (Ceratophyllum demerswri) and Musk-grass (Chara spp.) would 

 become dominant. At this point, a drawdown would be initiated to set back plant succession. 



Despite successful dewatering and drying, annual grasses did not always appear in the brackish 

 semi-impoundments. In these areas, dwarf spikerush and some flatsedges were often the only 

 desirable plants to germinate in response to a drawdown. According to Prevost (1987), soils in 

 brackish marshes should be maintained in a saturated or moist condition to prevent the 

 development of acid conditions which reduce germination of annuals and other desirable perennials. 

 At conditions conducive to the LPWMA, however, extensive drying was necessary to consolidate 

 bottom sediments and produce proliferation of aquatic vegetation (Joanen and Glasgow 1965). 

 When reflooded with freshwater, ponds soon filled with desirable freshwater aquatic plants. If 

 refilled with brackish water, widgeon grass and dwarf spikerush often filled ponds. 



During the dewatering process, deeper pond bottoms were temporarily dried, then refilled by 

 occasional showers (Figure 3). Upon reflooding, aquatic plants often flourished in deeper pond 

 areas while annuals flourished in shallower ponds, a situation most desirable for waterfowl use and 

 hunting. In 6 out of 12 years, successful drawdowns were achieved at LPWMA through late spring 

 and early summer droughts. The ability to achieve specific water level management goals was 

 largely weather dependent. As a result, management plans were frequently modified during the 

 course of any given year. 



Water Level and Salinity Stabilization 



The purpose of stabilization management was to maintain relatively constant conditions for the 

 growth of submerged aquatic plants and the survival of freshwater finfishes and estuarine organisms. 

 Stabilization management was usually conducted for at least two consecutive years after a 

 drawdown. Under stable conditions, submerged aquatic plants grew best in fresher semi- 

 impoundments the year following a drawdown. Similar observations were made by Harris and 

 Marshall (1963) and Linde (1969). Submerged aquatic plants grew best in brackish semi- 

 impoundments immediately following reflooding. Stabilization management was terminated when 

 undesirable aquatic vegetation became dominant. 



Water exchange was allowed to the maximum extent possible, provided that management goals 

 were not compromised. Water exchange, however, was often restricted to maintain stable aquatic 

 conditions during adverse meteorologic and/or hydrologic conditions. Flap gates were closed during 

 periods of drought and stop-logs were set to marsh level to protect against rising salinities and 

 falling water levels. Flap gates were occasionally closed to prevent turbid outside waters from 

 entering semi-impoundments and retarding growth of submerged aquatics. During periods of high 

 rainfall, stop-logs were removed and flap gates were operated to keep water levels from standing 

 over the marsh floor. With water standing on the marsh, decomposition of marsh vegetation 

 created oxygen depletions, often resulting in fish kills. 



290 



