GEOLOGY AND WATER RESOURCES NEAR MONTE CRISTI. 179 



Although the beds are thin and many of them discontinuous, some of the 

 Miocene rocks are sufficiently porous to contain considerable quantities of 

 water; and although no continuous thick beds of shale or other impervious 

 rocks are known in the Miocene series, shaly beds are known that would be 

 adequate retaining agents if advantageously placed with respect to a water- 

 bearing stratum. In the area under consideration the water table lies 

 close to the surface, so that the downward pressure of the water itself 

 might take the place of a retaining agent and produce weak artesian condi- 

 tions, but the flow under such conditions would not be very strong. It 

 seems probable that artesian conditions may exist at some places near 

 Monte Cristi, but whether adequate flows of suitable water could be ob- 

 tained at moderate depths at such places can not be predicted from the data 

 available. Artesian wells would have to be drilled to a greater depth than 

 wells from which the water is obtained by pumping. 



CONCLUSIONS AND RECOMMENDATIONS. 



Ground water can be obtained at no great depth in the lower part of the 

 valley of Rio Yaque, and pumped wells may yield it in considerable 

 quantity. Although the upper ground water is more or less salty, water 

 of good quality for both domestic use and irrigation can probably be ob- 

 tained, and as such water is far less contaminated than the river water it 

 will be preferable to the river water for domestic use. A much larger area 

 might be irrigated by water from wells than by water drawn from Rio 

 Yaque by present methods if the water should be suitable for irrigation, 

 and as the water table is at many places only a little farther below the sur- 

 face of the ground than the water in Rio Yaque is below the tops of the 

 river banks, the cost of pumping from wells would be hardly greater than 

 the cost of pumping from the river. If only water for domestic use is 

 desired, wells equipped with windmills would furnish an adequate supply 

 at a very low cost. Adequate supplies for watering stock could probably 

 also be obtained in this manner, but sufficient water for irrigation on 

 only a very small scale could be obtained with windmills. 



Definite information concerning the amount and quality of water and the 

 depth at which it would be encountered can be obtained only by drilling 

 test wells. Water will be encountered at a shallow depth, but the drill 

 must be sunk considerably deeper to obtain it in large quantity. As the 

 rocks that underlie the valley are thin bedded and are of various types 

 their water-bearing capacity will vary considerably both laterally and 

 in depth. The quality of the water will also vary, and the first water 

 encountered will probably be more saline than the deeper water. 



Test wells might be sunk on government property — for instance, at the 

 agricultural experiment farm — but the well should be drilled to a depth of 

 100 meters unless an adequate supply of water of satisfactory quality is 



