Polder I im Hochwasserrückhaltebecken Salzderhelden, nature reserve in Lower Saxony, Germany

Polder I im Hochwasserrückhaltebecken Salzderhelden is a protected area in Lower Saxony consisting of grasslands, water surfaces, and reed beds along the Leine river valley. The roughly 523-hectare site features shallow ponds, deeper water barriers, and reed-lined banks that create distinct ecological zones.

The area was placed under protection on 16 September 1995 as nature reserve NSG BR 097, managed by the Northeim district authority. It lies within the dykes of the Salzderhelden flood retention basin, which holds back the Leine during high water. In 2011 conservation measures at the gravel trap in the southern part added gravel banks as resting and breeding ground for birds.

The site's name reflects its dual purpose of flood control and nature conservation in the Leine valley. Visitors encounter a landscape shaped by human design to protect both wildlife and nearby settlements.

The site is open to visitors with walking paths and observation points including viewing platforms for watching birds without disturbing wildlife. Water levels change significantly with seasons, so careful footing near the banks is especially important during periods of high water.

The southern section holds a Geschiebesperre, a gravel trap where the Leine was widened to slow the current so stones and sediment from the Leine and the Rhume settle there instead of silting up the Salzderhelden barrage. The resulting shallow water attracts waders such as dunlin, ruff and black-tailed godwit on passage.