The research has hit a wall, but 'reaching where the water ends' often signals a fresh start.
Tips
history
From Wang Wei's (王维, Tang dynasty) 《终南别业》: 行到水穷处，坐看云起时 — 'I walk to where the water ends, then sit and watch the clouds rise.' Wang Wei — the Buddhist painter-poet — turns a hike up the Zhongnan mountains into a koan: at the apparent dead end, a new scene opens from above.
usage
Almost always quoted with its other half 坐看云起时. The couplet is invoked in modern Chinese to console someone facing an apparent dead end: the exhausted stream only means cloud-birth is near.
