Estimates indicate that the aquifer contains enough water to fill Lake Huron, but unfortunately, under the semiarid climatic conditions that presently exist in the region, rates of addition to the aquifer are minimal,amounting to about half a centimeter a year.
Estimates indicate that the aquifer contains enough water to fill Lake Huron, but unfortunately, under (that presently exist in the region)the semiarid climatic conditions , rates of (to the aquifer) addition are minimal,amounting to about half a centimeter a year.
估计表明含水层有足够的水去填充Huron湖，但是不幸的是，在（这区域最近的）半干旱气候条件下，（含水层的）增长速率是很小的，含水层一年大概增长1cm。
转折逻辑：含水层有水可以填冲，但是因为半干旱气候所以增长速率小。
因果：因为半干旱气候所以增长速率小。
Despite the current impressive size of the Ogallala aquifer, the region's climate keeps the rates of water addition very small.
虽然含水层有最近有可观的大小，但是区域的气候使得水的增速小。
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Although the aquifer has been adding water at the rate of only half a centimeter a year, it will eventually accumulate enough water of fill Lake Huron.
Although the aquifer (at the rate of only half a centimeter a year)has been adding water , it will eventually accumulate enough water of fill Lake Huron.
尽管含水层（仅以每年1cm的速度）增长，但是最后含水层会积累到足够填充Lake Huron的水。
------逻辑关系反了，原文强调增长速度慢
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Because of the region's present climatic conditions, water is being added each year to the aquifer.
因为区域最近的气候条件，所以水每年都会加入到含水层中去。
------因果关系不对，不是因为气候条件使得加水，而是气候条件使得加水速率慢。
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Even when the region experiences unfortunate climatic conditions, the rates of addition of water continue to increase.
甚至区域经历不好的气候条件时，水的增速也会持续增加。
---------逻辑不对，强调水增速慢