In contrast to canal spillage, canal seepage typically varies slowly with time, but in most cases has high spatial variability. Our approach to seepage testing depends primarily on the scope of the lining program. For projects addressing only a few candidate reaches, the preferred approach is to test each reach. For programmatic efforts were the objective is to prevent the largest volume of seepage with the least amount of money, we design strategic seepage testing programs. Such programs involve identification of seepage "drivers", segmenting the canal in reaches according to the identified drivers, and then testing an adequate number of representative reaches to support systemwide estimates through inference modeling. In nearly all cases, ponding tests are the preferred test method. In special cases, inflow-outflow measurement tests can provide satisfactory results.
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