Extract reservoir surface area in GEE

//this JavaScript code will generate a file containing the surface area of reservoirs in Landsat imagery available with <1% cloud coverage over the reservoir area

var reservoirs = ee.FeatureCollection('users/gufacincani/Don_Pedro');
//here Don_Pedro is the shapefile containing the borders of Don Pedro Reservoir

var reservoirs_geo = reservoirs.geometry()
var reservoirs_geo = reservoirs_geo.buffer(150); // Apply the 150-m buffer method to the Polygon object (reservoir) to make sure no water area is left out.

Map.addLayer(reservoirs, {color: 'red'}, 'Reservoirs');
//Map.addLayer(reservoirs_geo, {color: 'blue'}, 'Reservoirs2');

// 2. Get Landsat data.
var l8 = ee.ImageCollection('LANDSAT/LC08/C01/T1_TOA')//change to 'LANDSAT/LT05/C01/T1_TOA' for Landsat 5
                            .filterBounds(reservoirs_geo)//.filter(ee.Filter.lt('CLOUDY_PIXEL_PERCENTAGE',20))
                            .filterDate('2013-01-01','2021-12-31');//adapt dates for each Landsat

var c = l8.filterBounds(reservoirs_geo);

var withCloudiness = c.map(function(image) {
  var cloud = ee.Algorithms.Landsat.simpleCloudScore(image).select('cloud');
  var cloudiness = cloud.reduceRegion({
    reducer: 'mean', 
    geometry: reservoirs_geo, 
    scale: 30,
  });
  return image.set(cloudiness);
});

var filteredCollection = withCloudiness.filter(ee.Filter.lt('cloud', 1)); //get images with basically no cloud cover (no more than 1%)
print(filteredCollection);

var waterThreshold = 0; 

// water function:
var waterfunction = function(image){
  //add the NDWI band to the image
  var ndwi = image.normalizedDifference(['B3', 'B6']).rename('NDWI');
  //get pixels above the threshold
  var water01 = ndwi.gt(waterThreshold);
  //mask those pixels from the image
  image = image.updateMask(water01).addBands(ndwi);

  var area = ee.Image.pixelArea();
  var waterArea = water01.multiply(area).rename('waterArea');

  image = image.addBands(waterArea);

  var stats = waterArea.reduceRegion({
    reducer: ee.Reducer.sum(), 
    geometry: reservoirs_geo, 
    scale: 30,
  });

  return image.set(stats);
};

var collection = filteredCollection.map(waterfunction);
print(collection);

Map.addLayer(collection)

var chart = ui.Chart.image.series({
  imageCollection: collection.select('waterArea'), 
  region: reservoirs_geo, 
  reducer: ee.Reducer.sum(), 
  scale: 30,
});
print(chart);