Water　stress　is　increasingly　intense　all　over　the　world　owing　to　rapid　economic　development　and　global　climate　change.　Floodwater　utilization　can　mitigate　water　shortages　and　provide　multiple　water　use　benefits.　The　priority　of　evaluating　the　utilization　status　and　potential　of　floodwater　should　be　taken　into　account　at　a　basin　scale.　However,　few　studies　have　focused　on　the　assessment　approach.　This　paper　argues　that　the　amount　of　available　floodwater　is　a　function　of　the　ability　to　regulate　and　utilize　floodwater,　and　that　floodwater　can　be　classified　into　two　parts:　unavailable　floodwater　and　available　floodwater.　Based　on　this　definition,　the　logical　relationships　among　current　floodwater　utilization　potential,　theoretical　floodwater　utilization　potential,　and　the　current　and　theoretical　amounts　of　available　floodwater　in　a　basin　were　derived　using　limit　analysis　theory.　The　concepts　and　evaluation　methods　of　basin　floodwater　utilization　were　unified　in　this　paper.　Finally,　the　status　and　potential　of　floodwater　utilization　of　the　Nansi　Lake　Basin　were　evaluated.　The　results　showed　that　the　current　and　theoretical　amounts　of　available　floodwater　were　1629–1808 million m3　and　2050–2155 million m3,　respectively,　and　the　current　and　theoretical　amounts　of　floodwater　utilization　potential　were　266–386 million m3　and　678–733 million m3,　respectively.　The　application　in　the　Nansi　Lake　Basin　offers　some　practical　information　for　assessing　floodwater　utilization　scientifically　and　provides　some　significant　guidelines　for　other　basins.　©　2019,　Springer-Verlag　GmbH　Germany,　part　of　Springer　Nature.