Scroll to specific sections
A simple each loop could make your code smaller, something like:

var elems = [
  $('#slides'),
  $('#rev_slider_2_1'),
  $('#clients')
];

$.each(elems, function (index, $elem) {
  var previous = index &gt; 0 : elems[index-1].id : null;
  var next = index &lt; elems.length-1 ? elems[index+1].id : null;
  $elem.on('mousewheel', function(event) {
    event.preventDefault();
    if (event.originalEvent.wheelDelta &gt;= 0 &amp;&amp; previous) {
        //console.log('Scroll up');
        goTo(previous);
    } else if (next) {
        //console.log('Scroll down');
        goTo(next);
    }
  });
});