The Ogallala aquifer is a sandstone formation that underlies some 583,000 square kilometers of land extending from northwestern Texas to southern South Dakota.(奥加拉拉含水层是一个砂岩地层，位于从德克萨斯州西北部延伸到南达科他州南部，约583000平方公里土地的地下。)
Extraction of water depends on two properties of the aquifer: porosity and permeability.(水的开采取决于含水层的两个性质：孔隙度和渗透性。)
Two million years ago, a cave-studded aquifer lay beneath an undulating plain of shallow, wooded valleys and rolling hills.(200万年前，在树木丛生的谷地和波状丘陵地带的起伏平原之下，是洞穴密布的地下蓄水层。)
This aquifer was named the Ogallala aquifer after the Ogallala Sioux Indians, who once inhabited the region.(这个含水层被命名为奥加拉拉含水层，以曾经居住在这个地区的奥加拉拉-苏族印第安人的名字命名。)
A groundwater reservoir from which water can be extracted is called an aquifer.(可以从中抽取水的地下蓄水层被称为含水层。)
But switch the source to a river or an aquifer, and the cost of a cubic meter of water can plummet to 10 to 20 cents, and farmers often pay far less.(如果从河流或地下取水，每立方米的成本可大幅降至10至20美分，农业用水的成本甚至更低。)
The aquifer which had once fed the wells was pronounced dry.(曾经给这些井提供水源的蓄水层已被宣告枯竭。)
Geologists eventually realized that the cause was Houston's withdrawal of fresh water from the aquifer located under the city.(地质学家最终认识到导致海平面上升的原因是，休斯顿从城市地下的含水土层抽取淡水。)
This discovery forced city officials to use nearby Lake Houston and Lake Conroe for municipal water instead of the aquifer.(这项发现迫使城市官方用邻近的休斯顿湖和康罗湖代替含水土层，成为该市主要水源。)
Tapping the drought-prone region's aquifer for nonessential uses diverts water from farmers who need it desperately.(在这个干旱区域，这些没有用在刀刃上的水正是那些农民极度渴望的。)
