Identify the source of Irrigation that has recorded the maximum incidence of…

Concept. A source records negative growth in a year when its net irrigated area is lower than its own figure for the immediately preceding year. "Maximum incidence" asks how OFTEN that happens — the number of falling year-on-year intervals — not how large any single fall is. Nine years are listed, so every column is scored over the same eight consecutive intervals, and a figure that repeats unchanged counts as zero growth, not as a fall.

Application. Walking each offered column from 1997-98 to 2005-06 and marking every interval whose figure is lower than the one before it (all values in thousand hectares):

Cross-check. Three points settle the count before it is accepted:

• Private canals stay at 206 in 2003-04 and again in 2004-05; an unchanged figure is zero growth, not a fall, so those two intervals must not be added to the tally.

• If "maximum incidence" were misread as the biggest single fall rather than the most frequent fall, the choice still does not change on absolute terms: the largest one-year drop in any of the irrigation-source columns is 1,168 (15,031 in 2001-02 down to 13,863 in 2002-03), and it sits in the government canals column. The Total column falls further over that same interval, by 2,894, but a total is not itself a source of irrigation.

• Tanks appears in the table but is not offered as a choice; it too falls five times, so the question is settled among the four sources actually offered.

Result. Counting falling intervals, government canals record negative growth in five of the eight intervals, the highest count among the sources offered, so government canals is the answer.