Reading a Climate Graph to Judge Agricultural Viability
A region has mean monthly temperatures (°C) of 26, 26, 24, 20, 16, 13, 12, 14, 17, 20, 23, 25 and mean monthly rainfall (mm) of 8, 10, 15, 45, 90, 120, 110, 85, 60, 35, 18, 10. A development agency proposes growing a high-value crop that needs at least 500 mm of rain during its 5-month growing season and cannot tolerate more than two consecutive months below 10 °C. A farmer wants to grow it year-round. A hydrologist warns about a dry summer.
1. Calculate the annual rainfall and identify the growing season, then judge whether the crop can be grown as the farmer proposes.
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Annual rainfall = 8+10+15+45+90+120+110+85+60+35+18+10 = 606 mm.
Rainfall is strongly seasonal: the wettest five months (May–September) total 90+120+110+85+60 = 465 mm, and even including April (45 mm) gives 510 mm. The dry half (October–March) totals only 8+10+15+35+18+10 = 96 mm.
Temperature constraint: months below 10 °C? The minimum is 12 °C (July), so no month falls below 10 °C. The two-consecutive-month rule is satisfied everywhere.
So the crop can be grown, but only if its 5-month growing season aligns with May–September, when rainfall (465 mm) is close to but slightly under the 500 mm requirement. The farmer's year-round plan is not viable: October–March offers only 96 mm, far short of what the crop needs. The crop is climatically possible in the wet season but requires either supplementary irrigation of roughly 35 mm across the season or a shift to a slightly earlier start (April–August = 510 mm) to clear the 500 mm threshold.
2. Evaluate the hydrologist's warning and explain how it should shape the agency's recommendation.
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The hydrologist is correct but incomplete. The data confirm a pronounced dry summer: October–March receives 96 mm, about 16% of annual rainfall, with December–February the driest (10–18 mm). For a crop needing 500 mm in-season, summer planting would fail without heavy irrigation, and even wet-season planting leaves a small deficit.
The warning should shape the recommendation in three ways. First, the agency should specify a May–September planting window, not year-round. Second, it should quantify the irrigation gap (~35 mm) and confirm water availability, since the dry summer means stored water is the binding constraint. Third, it should flag inter-annual variability: monthly means hide drought years, so a single dry season could halve the wet-season total.
A balanced recommendation is: the crop is viable as a seasonal, irrigated enterprise with a confirmed water source and drought contingency, but not as the farmer's year-round proposition. The agency should present the climate graph honestly, showing both the wet-season opportunity and the summer risk.