Rhea P. Williams 1979 <p><span>Sediment </span><span>data </span><span>collected </span><span>in </span><span>the </span><span>Santa </span><span>Clara </span><span>River </span><span>basin </span><span>during </span><span>the </span><span>1967-75 </span><span>water </span><span>years </span><span>were </span><span>analyzed </span><span>to </span><span>determine </span><span>the </span><span>particle </span><span>size </span><span>and </span><span>quantity </span><span>of </span><span>sediment </span><span>transported </span><span>past </span><span>three </span><span>gaging </span><span>stations. </span><span>The </span><span>total </span><span>sediment </span><span>discharge </span><span>of </span><span>the </span><span>basin, </span><span>computed </span><span>from </span><span>records </span><span>of </span><span>Santa </span><span>Clara </span><span>River </span><span>at </span><span>Montalvo </span><span>for </span><span>water </span><span>years </span><span>1968-75, </span><span>was </span><span>63 </span><span>. 5 </span><span>million </span><span>tons, </span><span>of </span><span>which </span><span>59.5 </span><span>million </span><span>tons </span><span>was </span><span>carried </span><span>in </span><span>suspension </span><span>and </span><span>an </span><span>estimated </span><span>4 </span><span>million </span><span>tons </span><span>was </span><span>transported </span><span>as </span><span>unsampled </span><span>sediment </span><span>discharge. </span><span>About </span><span>17. </span><span>7 </span><span>million </span><span>tons, </span><span>or </span><span>28 </span><span>percent </span><span>of </span><span>the </span><span>total </span><span>sediment </span><span>discharge, </span><span>was </span><span>coarse </span><span>sediment </span><span>(particles </span><span>larger </span><span>than </span><span>O. </span><span>062 </span><span>millimeter). </span></p><p><span>Most of the sediment was transported during only a few days of floodflow each year. During the 1968-75 water years, approximately 55 percent of the total sediment was transported in 2 days and 92 percent was transported in 53 days. </span></p><p><span>The </span><span>long-term </span><span>(1928-75) </span><span>average </span><span>annual </span><span>sediment </span><span>discharge </span><span>of </span><span>the </span><span>Santa </span><span>Clara </span><span>River </span><span>at </span><span>Montalvo </span><span>is </span><span>estimated </span><span>at </span><span>3.67 </span><span>million </span><span>tons. </span><span>Of </span><span>that </span><span>quantity, </span><span>2.58 </span><span>million </span><span>tons </span><span>consisted </span><span>of </span><span>fine </span><span>sediment </span><span>and </span><span>1.09 </span><span>million </span><span>tons </span><span>consisted </span><span>of </span><span>coarse </span><span>sediment. </span></p><p><span>A </span><span>sediment </span><span>budget </span><span>for </span><span>the </span><span>Santa </span><span>Clara </span><span>River </span><span>basin </span><span>was </span><span>estimated </span><span>for </span><span>sediment </span><span>discharges </span><span>under </span><span>both </span><span>natural </span><span>and </span><span>actual </span><span>conditions. </span><span>The </span><span>major </span><span>difference </span><span>between </span><span>natural </span><span>and </span><span>actual </span><span>sediment </span><span>discharges </span><span>of </span><span>the </span><span>Santa </span><span>Clara </span><span>River </span><span>basin </span><span>is </span><span>the </span><span>sediment </span><span>intercepted </span><span>upstream </span><span>from </span><span>Lake </span><span>Piru. </span><span>The </span><span>combined </span><span>trap </span><span>efficiency </span><span>of </span><span>Lake </span><span>Piru </span><span>and </span><span>Pyramid </span><span>Lake </span><span>approaches </span><span>100 </span><span>percent. </span><span>Sediment </span><span>deposited </span><span>in </span><span>these </span><span>reservoirs </span><span>resulted </span><span>in </span><span>about </span><span>a </span><span>6-percent </span><span>reduction </span><span>of </span><span>sediment </span><span>to </span><span>the </span><span>Santa </span><span>Clara </span><span>River </span><span>basin </span><span>during </span><span>the </span><span>historical </span><span>period </span><span>(1928-75) </span><span>and </span><span>a </span><span>12-percent </span><span>reduction </span><span>during </span><span>the </span><span>period </span><span>most </span><span>affected </span><span>by </span><span>dams </span><span>(1953-75). </span><span>Sediment </span><span>losses </span><span>to </span><span>the </span><span>basin </span><span>by </span><span>gravel </span><span>mining, </span><span>diversion </span><span>of </span><span>flows, </span><span>and </span><span>interception </span><span>of </span><span>sediment </span><span>in </span><span>the </span><span>Castaic </span><span>Creek </span><span>basin </span><span>resulted </span><span>in </span><span>additional </span><span>reductions </span><span>of </span><span>2 </span><span>percent </span><span>during </span><span>the </span><span>period </span><span>1928-75 </span><span>and </span><span>4 </span><span>percent </span><span>during </span><span>the </span><span>period </span><span>1953-75.</span></p> application/pdf 10.3133/wri7978 en U.S. Geological Survey Sediment discharge in the Santa Clara River Basin, Ventura and Los Angeles Counties, California reports