In the dry season a lot of blue water is used by vegetation.
Use the code below to make the distinction between Blue an Green water used for evapotranspiration.
//SERVIR-MEKONG 2016 //AUTHORS: Ate Poortinga //CONTACT INFORMATION: //Date: //LINK TO REFERENCE SCRIPT(S): //LINK TO REPORT(S): ////////////////////// //BUILD: Land Cover //PURPOSE: //SENSORS: ///////////////////////////////////////////////////////////////// ///////////////////////////////////////////////////////////////// // User specified parameters // Data // import ET data var ET = ee.ImageCollection("users/atepoortinga/MekongEtdata") // setup the vizualization var et_viz = {min:0.0, max:150, palette:"000000,0000FF,FDFF92,FF2700,FF00E7"}; // Data // variables for start and end year var startyear = 2006; var endyear = 2006; var months = ee.List.sequence(1,12); // variables for start and end month var startmonth = 1; var endmonth = 1; // define start and end date var startdate = ee.Date.fromYMD(startyear,startmonth,1); var enddate = ee.Date.fromYMD(endyear+1,endmonth,1); // create list for years var years = ee.List.sequence(startyear,endyear); // polygon for the red river var Ca = ee.FeatureCollection('ft:11uQewh4u7NFXneH99YPs6P9F1Au6wxBq959BZWt_','geometry'); // set visualizaton parameters var et_viz = {min:0.0, max:200, palette:"000000,0000FF,FDFF92,FF2700,FF00E7"}; // Functions // select ET for time range var ET = ET.filterDate(startdate, enddate) // Sort chronologically in descending order. .sort('system:time_start', false) .filterBounds(Ca); // select P for time range var P = chirps.filterDate(startdate, enddate) // Sort chronologically in descending order. .sort('system:time_start', false) .filterBounds(Ca); // calculate the et for each month var allET = ee.ImageCollection.fromImages( years.map(function (y) { return months.map(function(m){ var w = ET.filter(ee.Filter.calendarRange(y, y, 'year')) .filter(ee.Filter.calendarRange(m, m, 'month')) .sum(); return w.set('year', y) .set('month', m) .set('date', ee.Date.fromYMD(y,m,1)) .set('system:time_start',ee.Date.fromYMD(y,m,1)) }); }).flatten()); // calculate the P for each month var allP = ee.ImageCollection.fromImages( years.map(function (y) { return months.map(function(m){ var w = P.filter(ee.Filter.calendarRange(y, y, 'year')) .filter(ee.Filter.calendarRange(m, m, 'month')) .sum(); return w.set('year', y) .set('month', m) .set('date', ee.Date.fromYMD(y,m,1)) .set('system:time_start',ee.Date.fromYMD(y,m,1)) }); }).flatten()); // combine the two datasets var myCollection = allP.combine(allET); print(myCollection) // calculate the Incremental ET myCollection = myCollection.map(function(img){ var myimg = img.expression("(p - et) ", { p: img.select("precipitation"), et: img.select("b1"), }); myimg = myimg.lt(0).multiply(myimg).multiply(-1) return img.addBands(myimg.rename('incrementalET')); }) print(myCollection) var viz = {min:0.0, max:1000, palette:"ff0000,ff8800,fffa00,4cff00,00ffe1,0400ff,ff00ff"}; Map.addLayer(myCollection.select('incrementalET').sum().clip(Ca),viz,"incremental ET"); // landuse map var luse = ee.FeatureCollection('ft:1Hgt_gN4R7opnaFxamqJsJnkic_WWunxgbBtHsT5J','geometry'); // Predefine the chart titles. var title = { title: 'ET', hAxis: {title: 'Time'}, vAxis: {title: 'ET (mm)'}, }; // setup the chart var chart = ui.Chart.image.seriesByRegion(myCollection, luse, ee.Reducer.mean(), 'b1', 2500, 'system:time_start', 'landuse') .setOptions(title) .setChartType('ColumnChart'); // plot the chart print(chart) // Predefine the chart titles. var title = { title: 'Incremental ET', hAxis: {title: 'Time'}, vAxis: {title: 'ET incremental (mm)'}, }; // setup the chart var chart = ui.Chart.image.seriesByRegion(myCollection, luse, ee.Reducer.mean(), 'incrementalET', 2500, 'system:time_start', 'landuse') .setOptions(title) .setChartType('ColumnChart'); // plot the chart print(chart) // center the map Map.centerObject(Ca, 5);