02118nas a2200157   4500008004100000245008000041210006900121300001400190490000700204520160200211653005201813100001701865700001501882700001401897856004901911       2002                        eng d00aFreshwater requirements of a semi-arid supratidal and floodplain salt marsh0 aFreshwater requirements of a semiarid supratidal and floodplain   a1394-14050 v253 aWhen rivers are impounded, the reduction in downstream flow can produce important and often adverse effects, especially in the estuarine environment. One or more dams have been proposed for the Olifants River system in the Western Cape, South Africa. This estuary has an extensive area of salt marsh that was examined to see whether it required occasional flooding with freshwater to wash out accumulated salts. The dominant salt marsh species, Sarcocornia pillansii, occurred in supratidal and floodplain areas where the water table was shallowest, the soil moisture highest, and the soil electrical conductivity lowest. Aerial photographs and simulated runoff data showed that no flood had covered the floodplain during the previous 80 years. The data indicate that salt marsh plants use saline groundwater during the dry months of the year in order to survive, but use the short season winter rainfall period with low salinity conditions to grow and reproduce. This study demonstrated that live roots of S. pillansii reached the water table during the dry season. Tissue and soil water potentials, the relationship between vegetation cover, depth to the water table, and electrical conductivity of the groundwater support the conclusion that saline groundwater is the only source of water during the drier months of the year. Freshwater flooding of the river in winter may be important because it covers the supratidal area with less saline water and reduces the depth to the water table on the floodplain. This makes the groundwater more accessible to the halophytes growing on the floodplain.10aSouth Africa, salt marsh, Sarcocornia pillansii1 aBornman, T G1 aAdams, J B1 aBate, G C  uhttps://juncaginaceae.myspecies.info/node/29