referring to fig1 of the drawings , the canal paving machine of the present invention , designated generally at 10 , includes an elongated frame means 12 that extends transversely across a canal 14 having water 16 ( fig2 and 3 ) flowing therein , and driven endless tracks 18 and 20 at the ends thereof for moving the frame means 12 along the canal 14 . hydraulic cylinders 15 interconnect the frame means 12 and the tracks 18 and 20 and function to raise and lower the frame means 12 relative to the tracks 18 and 20 . an upper deck 22 is mounted on the frame means adjacent one end thereof for supporting a power source such as a diesel engine 24 and control console 26 to define an operator station 28 therebetween . a vertically moveable concrete paving assembly is designated generally at 44 to apply a layer of concrete 46 to the bottom of the canal 14 ( fig2 and 3 ) hinged dam members 48 , 50 , and 52 on the frame means 12 ( fig1 - 4 ) hang downwardly like curtains at positions forwardly of , to one side of , and rearwardly of the concrete paving assembly 44 , to reduce the flow of water in the concrete laying area of the concrete paving assembly 44 and thereby protect the concrete being applied to the canal bottom from the water current in the canal . the concrete paving assembly 44 is operated from operator &# 39 ; s station 28 , to continuously apply a concrete layer to approximately one - half of the bottom of the canal 14 on travel of the machine in one direction along the length of the canal . the canal paving assembly 44 as shown in fig5 , 8 , and 9 , includes a hopper 76 formed with a forward wall 78 and a rearward wall 80 and having a generally horizontally disposed inner section 75 and an outer upwardly inclined section 77 which follow the confirmation of the canal bottom and adjacent side slope 40 of the canal 14 . a series of vertical baffles , one of which is illustrated at 34 in fig9 extend transversely of and in a spaced relation longitudinally of the forward and rearward walls 78 and 80 to help maintain a desired level of the concrete within the hopper 76 . an auger 82 ( fig5 , and 8 ) coextensive in length with the hopper 76 and positioned therein above the baffles 34 , is operated to move concrete in a direction from the horizontal section 75 upwardly into the inclined hopper section 77 to maintain a selected concrete material head pressure on the concrete within the hopper 76 . the auger 82 is comprised of a horizontal auger portion 82a and an inclined auger portion 82b operatively associated with the hopper sections 75 and 77 , respectively . the longitudinal axis of auger portion 82a , therefore , is parallel with the bottom of the hopper section 75 along the horizontal portion of the canal bottom . inasmuch as the water pressure at the bottom of the hopper 76 decreases as the hopper 76 rises along the sloped side wall portion 40 , due to the decreasing depth of the water along the slope of the canal , auger portion 82b is not disposed parallel to the bottom of the hopper 76 , but is inclined with respect thereto as seen in fig6 to maintain the desired concrete head pressure in the hopper section 77 . a conveyor 84 , shown in fig2 and 3 , h -. as an outer end 92 pivoted on the frame means 12 and extends from such outer end through the frame means 12 and inwardly over the length of the hopper 76 . concrete is supplied to the outer conveyor end 92 from trucks or the like . concrete deposited on the outer end 90 of the conveyor 84 is conveyed toward the inner end thereof . a diverter car 85 , mounted for movement longitudinally of the conveyor 84 progressively diverts concrete from the conveyor 84 into the hopper 76 . hopper 76 ( fig5 ) is supported for up and down vertical movement on the frame means 12 by a plurality of hydraulic cylinders 90 . during a concrete applying operation , the hopper 76 will remain at a generally constant level above the canal bottom . however , when a pour of concrete is terminated , the hopper 76 must be raised out of the water to enable the removal of the concrete therein . raising of the hopper 76 out of the water is also necessary for servicing and maintenance purposes or when the paving machine is manipulated through a 180 degree turn for a reversed travel along the canal to apply a concrete layer to the unfinished half of the canal bottom . forward and rearward movement of the hopper 76 relative to the frame means 12 is limited by a plurality of cylinders 124 ( fig5 ) which are interconnected between the concrete forming assembly 44 and the frame means 12 . the cylinders 124 are adjustable to center and then stabilize the hopper 76 vertically relative to the frame means 12 . the lower or discharge end 104 of the hopper 76 is selectively opened and closed by means of a horizontally moveable gate means 94 which is operatively connected to a plurality of horizontally slideable tubular frame members 95 that are telescopically received within tubes 98 secured to the hopper 76 as seen in fig8 and 9 . one end of each of the frame members 95 is connected to a bar 100 and the opposite end thereof is secured to the gate means 94 as seen in fig9 . the bar 100 has a plurality of hydraulic cylinders 102 operatively connected thereto so that the bar 100 may be selectively horizontally moved . the selective horizontal movement of the bar 100 causes the gate 94 to be moved relative to the discharge end 104 of the hopper 76 between the positions illustrated in solid and broken line in fig8 to selectively open and close the same . the head pressure of concrete in the hopper 76 exceeds the water pressure at the bottom of the canal so that concrete flows through the gate 94 when it is in its open position therefor without any backflow of water into the hopper 76 . a surge plate 106 is provided below the gate means 94 and extends horizontally forwardly therefrom to prevent any &# 34 ; boiling up &# 34 ; of the canal bottom in the event it is soft in advance of the concrete being deposited on the canal bottom . the surge plate 106 is pivotally connected at 107 to the hopper means 76 . the angular position of the surge plate 106 is permitted a limited range of floating movement by a surge plate cylinder 109 which is mounted at the forward end of a cantilevered beam 111 which extends forwardly from the forward wall 78 of the hopper 76 . a plurality of hydraulic vibrators 110 are provided in the lower end of the hopper 76 to vibrate the concrete being applied to the canal bottom to ensure uniform density of the concrete being applied and to assist in the outflow of concrete through the discharge end 104 of the hopper 76 . a screed 112 is provided at the lower end of the rearward wall 80 to apply the concrete uniformly on the canal bottom . screed 112 is comprised of a flat section 112a which extends over the flat bottom portion of the canal and a sloped side portion 112b which extends over the sloped side wall portion of the canal . the horizontal portion 112a is flat to form a smooth finish to the concrete applied to the canal bottom . the sloped side wall portion 112b of the screed is provided with a plurality of notches 113 to form a plurality of animal escape steps 115 on the sides of the canal , as shown in fig6 and 7 . dam member 52 is pivotally connected at its upper end to frame means 12 at 114 ( fig5 ). a plurality of hydraulic cylinders 116 are connected to the frame means 12 and the dam member 52 so that the dam member 52 may be moved from an operative vertical position , illustrated by solid lines in fig5 to an inoperative substantially horizontal position illustrated by broken lines in fig5 . the lower end of dam member 52 terminates at a point above the surface of the concrete which has been deposited or laid on the canal bottom . dam member 48 is connected at its upper end to the forward end of frame means 12 at 118 . a plurality of hydraulic cylinders 120 permit the dam member 48 to be pivotally raised and lowered with respect to the frame means 12 as desired . a plurality of hydraulic cylinders 122 pivotally interconnect the frame means 12 with the dam member 48 to enable the dam member 48 to be pivotally moved between a vertical operating position and the substantially horizontal rest position illustrated in fig1 . dam member 50 is connected at its upper end to frame means 12 at 124 and is provided with a plurality of hydraulic cylinders 126 similar to cylinders 120 to enable dam member 50 to be moved relative to the frame means 12 and the canal bottom ( fig2 and 3 ). a plurality of hydraulic cylinders 128 pivotally interconnect dam member 50 with frame means 12 to enable the dam member 50 to be pivotally moved between the substantially horizontal position illustrated in fig2 to a vertical or hanging operative position . when the dam members 48 , 50 , and 52 are in their vertical positions , they cooperate to shield the lower end of the paving apparatus from water current in the canal . to lay concrete on one - half of the canal bottom , the concrete hopper 76 is raised and then charged with concrete by way of the conveyor 84 . the auger 82 is operated to distribute the concrete evenly in the hopper 76 to the appropriate level corresponding to the desired pressure head of concrete . the concrete laying apparatus is then lowered into position over approximately one - half of the canal bottom . the cylinders 90 and 124 are used to lower the concrete laying apparatus 44 to the appropriate vertical position centered relative to the frame 12 . sensors and / or visual observation by divers may be used to assure appropriate positioning . the lining operation begins upon opening of the gate 94 and movement of the apparatus forwardly . the vibrators 110 are operated to assist in the flow of concrete of uniform density through the discharge end 104 . because the apparatus blocks only approximately one - half of the canal during operation , the water flow in the canal is not significantly affected . a layer of concrete is placed over the side wall 40 and the canal bottom to approximately the center line of the canal . upon the return pass , wherein the apparatus is turned around and moving in the opposite direction , the concrete laying apparatus will be allowed to pour concrete completely to the edge of the previously laid concrete layer at the center of the canal bottom 38 to form a completely solid concrete layer over the canal bottom . when the apparatus is to be shut down such as at the end of a shift or if the apparatus is to be turned around for a return pass , the gate 94 is closed and the vibrators 110 turned off . it is then necessary to remove the concrete from the hopper 76 before the same hardens therein . the hopper 76 is vertically moved upwardly by means of the hydraulic cylinders 90 . a barge or other suitable means is then moved into position beneath the concrete hopper 76 . the gates 94 are then opened to permit any concrete in the hopper 76 to flow downwardly therefrom into the barge or other receptacle . whereas the machine of the present invention has been shown and described in connection with the preferred embodiment thereof , it will be understood that modifications , substitutions , and additions may be made therein which are within the intended scope of the appended claims .