426 Transactions of the 



tional area one hundred and fifty square feet, and a discharge of three 

 hundred cubic feet per second. It will be observed tbat in comparison 

 with the rates of discharge above given for different rivers, the capacity 

 of these canals is from one tentb to one twentieth of each stream. 

 Thus, taking the sectional area of the San Joaquin River at its lowest 

 stage at three thousand square feet, and its rate of flow at two milgfi 

 per hour, we remark that its discharge (nine thousand cubic feet per 

 second j is equal to the combined capacity of fifteen canals, each thirty- 

 two feet on the bottom — the dimensions of the San Joaquin and King's 

 River Company's Canal, which takes its water from that stream. 



Recurring to the above table of the cachment areas and discharge of 

 the rivers of California, it is to be remarked that the actual discharge 

 is far below the theoretical. For the purposes of irrigation the discre- 

 pancy is not important, for the actual discharge is seen to be ten times 

 greater than can be applied to that purpose. But it is interesting to in- 

 quire what becomes of the water. We know the full amount that falls 

 in each cachment basin; we know that it does not flow off through the 

 visible drainage channel; the inference is inevitable that a great part of 

 it passes away through underground strata of gravel and other perme- 

 able composition. If this be true, Ave shall expect two things: first, 

 that the existence of such underground water-flow would be disclosed 

 by borings; and second, that some of these strata would be intersected 

 from time to time by the watercourses, which would then receive the 

 flow of each stratum, resulting probably in an appreciable increase in 

 the volume of 'water flowing in such channel. Both of these conditions 

 are found to exist in fact. In connection with the surveys for the canals 

 now under construction, extensive borings were made at the San Joaquin 

 River, its tributaries, and in the vicinity of Tulare Lake. In each in- 

 stance the existence of an extensive underground drainage was disclosed. 

 The fact that the main river courses receive accessions to their volume 

 of flow from these sources is familiarly illustrated throughout their 

 length. The San Joaquin, at Firebaugh's, runs one half more water than 

 it does at the railroad crossing, though in the interval it does not receive 

 a single tributary. King's River, at Kingston, flows double the volume 

 thatTt does at the upper ferry, and at the upper ferry it flows one half 

 more water than at Centerville, yet it receives no tributary. Other 

 streams that flow a large volume of water at one point, a few miles lower 

 are dry beds. In fact, there is scarcely a California stream that does 

 not illustrate the fact of underground drainage by one or both of these 

 classes of phenomena. 



Tulare Lake, and the drainage system in which it plays the part of 

 reservoir, illustrates underground drainage upon a great scale. During 

 a portion of the year the surface of this lake is raised sufficiently to 

 discharge by overflow the surplus of waters poured into it by Kern, 

 Tule, and King's Rivers, and Kaweah Creek. But after the waters have 

 subsided so that overflow ceases, those large rivers continue to discharge 

 into the lake an amount of water equal to the discharge of the Ameri- 

 can and Yuba Rivers and Cache Creek combined— exceeding many fold 

 the greatest possible amount of depletion by evaporation. Yet the lake 

 contrives to get rid of a greater amount of water than it receives; the 

 level of the surface is slowly lowered throughout the season; under- 

 ground drainage here becomes the only possible means of efflux; and 

 in fact the borings made adjacent to the lake disclose the existence of a 

 copious underground flow — the measure of which is indicated by the 

 combined influx from Kern and King's Rivers. When the levees shall 



