Erosion leading to sedimentation in surface water may disrupt aquatic habitats and deliver sediment-bound nutrients that contribute to eutrophication. Land use changes causing loss of native vegetation have accelerated already naturally high erosion rates in New Zealand and increased sedimentation in streams and lakes. Sediment-bound phosphorus (P) makes up 71–79% of the 17–19 t P y⁻¹ delivered from anthropogenic sources to Lake Rotorua in New Zealand. Detainment bunds (DBs) were first implemented in the Lake Rotorua catchment in 2010 as a strategy to address P losses from pastoral agriculture. The bunds are 1.5–2 m high earthen stormwater retention structures constructed across the flow path of targeted low-order ephemeral streams with the purpose of temporarily ponding runoff on productive pastures. The current DB design protocol recommends a minimum pond volume of 120 m³ ha⁻¹ of contributing catchment with a maximum pond storage capacity of 10 000 m³. No previous study has investigated the ability of DBs to decrease annual suspended sediment (SS) loads leaving pastoral catchments. Annual SS yields delivered to two DBs with 20 ha and 55 ha catchments were 109 and 28 kg SS ha⁻¹, respectively, during this 12-month study. The DBs retained 1280 kg (59%) and 789 kg (51%) of annual SS loads delivered from the catchments as a result of the bunds' ability to impede stormflow and facilitate soil infiltration and sediment deposition. The results of this study highlight the ability of DBs to decrease SS loads transported from pastures in surface runoff, even during large storm events, and suggests DBs are able to reduce P loading in Lake Rotorua.

中文翻译：

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滞留堤在地表径流中减少从牧区流域输送的沉积物的能力

导致地表水沉积的侵蚀可能会破坏水生栖息地，并提供导致富营养化的沉积物养分。导致本地植被丧失的土地利用变化加速了新西兰本来就很高的侵蚀率，并增加了溪流和湖泊中的沉积物。沉积物结合磷 (P) 占 17-19 t P y ^{-1 的}71-79%从人为来源运送到新西兰的罗托鲁瓦湖。2010 年，在罗托鲁瓦湖流域首次实施了滞留堤坝 (DB)，作为解决牧区农业磷损失的战略。堤坝是 1.5-2 m 高的土制雨水蓄水结构，横跨目标低阶短暂河流的流动路径，目的是暂时积蓄生产牧场的径流。当前的 DB 设计协议建议最小池塘容积为 120 m ³ ha ^-1的贡献集水区，最大池塘存储容量为 10 000 m ³. 以前没有研究调查 DBs 减少离开牧区集水区的年度悬浮泥沙 (SS) 负荷的能力。在这 12 个月的研究中，输送到两个 20 公顷和 55 公顷流域的 DB 的年 SS 产量分别为 109 和 28 kg SS ha ^-1。由于堤坝能够阻止暴雨流量并促进土壤渗透和沉积物沉积，因此 DB 保留了 1280 公斤（59%）和 789 公斤（51%）的年 SS 负荷，这些负荷是从集水区输送的。这项研究的结果突出了 DBs 降低地表径流中从牧场传输的 SS 负荷的能力，即使在大风暴事件期间，并表明 DBs 能够减少罗托鲁瓦湖的 P 负荷。