diff --git a/assets/src/scripts/monitoring-location/components/hydrograph/selectors/axes.js b/assets/src/scripts/monitoring-location/components/hydrograph/selectors/axes.js
index 8d2dd14f2bef9915901bc4356bdc451a051166b9..6c10444522449963c93c26e8c8867e709d0a8a75 100644
--- a/assets/src/scripts/monitoring-location/components/hydrograph/selectors/axes.js
+++ b/assets/src/scripts/monitoring-location/components/hydrograph/selectors/axes.js
@@ -9,7 +9,7 @@ import {getIVParameter} from 'ml/selectors/hydrograph-data-selector';
 
 import {getSecondaryYAxisTickDetails, getPrimaryYAxisTickDetails} from './domain';
 import {getLayout} from './layout';
-import {getXScale, getBrushXScale, getYScale, getSecondaryYScale} from './scales';
+import {getXScale, getBrushXScale, getYScale} from './scales';
 import {getPrimaryParameter} from './time-series-data';
 
 
@@ -69,8 +69,8 @@ export const getBrushXAxis = createSelector(
  */
 export const getAxes = memoize(graphKind => createSelector(
     getXScale(graphKind, 'current'),
-    getYScale(graphKind),
-    getSecondaryYScale(graphKind),
+    getYScale(graphKind, 'primary'),
+    getYScale(graphKind, 'secondary'),
     getPrimaryYAxisTickDetails,
     getSecondaryYAxisTickDetails,
     getLayout(graphKind),
diff --git a/assets/src/scripts/monitoring-location/components/hydrograph/selectors/scales.js b/assets/src/scripts/monitoring-location/components/hydrograph/selectors/scales.js
index 4310e57fe45f867c7f6fb96612195e7caf0590fd..c4dc630a0bc9f9129ed30e3d7b7ab35d5f930f3e 100644
--- a/assets/src/scripts/monitoring-location/components/hydrograph/selectors/scales.js
+++ b/assets/src/scripts/monitoring-location/components/hydrograph/selectors/scales.js
@@ -104,34 +104,26 @@ export const getBrushXScale = getXScale('BRUSH', 'current');
 
 /**
  * Selector for y-scale
+ * @param {String} graphKind -- indicates if the y-scale (axis) will be used on the hydrograph ('MAIN') or the timeframe
+ *      slider, AKA brush graph ('BRUSH')
+ * @param {String} dataKind -- indicates if the y-scale will be used with the primary y-axis ('primary') or secondary
+ *      y-axis ('secondary'). If not provided, it is assumed to be 'primary'
  * @param  {Object} state   Redux store
  * @return {Function}       D3 scale function
  */
-export const getYScale = memoize(graphKind => createSelector(
+export const getYScale = memoize((graphKind, dataKind) => createSelector(
     getLayout(graphKind),
     getPrimaryValueRange,
-    getPrimaryParameter,
-    (layout, yDomain, parameter) => {
-        return createYScale(parameter ? parameter.parameterCode : '', yDomain, layout.height - (layout.margin.top + layout.margin.bottom));
-    }
-));
-
-/**
- * Selector for secondary y-scale
- * @param  {Object} state   Redux store
- * @return {Function}       D3 scale function
- */
-export const getSecondaryYScale = memoize(graphKind => createSelector(
-    getLayout(graphKind),
     getSecondaryValueRange,
+    getPrimaryParameter,
     getSelectedSecondaryParameterCode,
-    (layout, yDomain, secondaryParameterCode) => {
-        return createYScale(secondaryParameterCode ? secondaryParameterCode.parameterCode : '', yDomain, layout.height - (layout.margin.top + layout.margin.bottom));
+    (layout, primaryYDomain, secondaryYDomain, primaryParameter, secondaryParameter) => {
+        const parameter = dataKind === 'secondary' ? secondaryParameter : primaryParameter;
+        const yDomain = dataKind === 'secondary' ? secondaryYDomain : primaryYDomain;
+
+        return createYScale(parameter ? parameter.parameterCode : '', yDomain, layout.height - (layout.margin.top + layout.margin.bottom));
     }
 ));
 
-
-
-
-export const getMainYScale = getYScale();
-export const getBrushYScale = getYScale('BRUSH');
+export const getMainYScale = getYScale('MAIN', 'primary');
+export const getBrushYScale = getYScale('BRUSH', 'primary');
diff --git a/assets/src/scripts/monitoring-location/components/hydrograph/selectors/time-series-data.js b/assets/src/scripts/monitoring-location/components/hydrograph/selectors/time-series-data.js
index 438042a54ff1b446d4899aca1f49c7bc1f70d3eb..8fa38151ff5c525c7f10fcd5a24f6a18b6d6860e 100644
--- a/assets/src/scripts/monitoring-location/components/hydrograph/selectors/time-series-data.js
+++ b/assets/src/scripts/monitoring-location/components/hydrograph/selectors/time-series-data.js
@@ -96,7 +96,13 @@ export const hasAnyVisibleData = createSelector(
     }
 );
 
-
+/**
+ * A Redux selector function that returns the title of the main hydrograph.
+ * @param {String} titleKind -- is either the title for the primary data ('primary'), which is always shown (if available)
+ *      or the secondary data ('secondary') if a secondary parameter is selected by the user. Defaults to 'primary' if argument
+ *      is not explicitly included.
+ * @returns {String} - the primary or secondary title for the main hydrograph
+ */
 export const getTitle = memoize(titleKind => createSelector(
     getPrimaryParameter,
     getSelectedPrimaryIVMethodID,
diff --git a/assets/src/scripts/monitoring-location/components/hydrograph/time-series-graph.js b/assets/src/scripts/monitoring-location/components/hydrograph/time-series-graph.js
index ff61065a74d26bb76241dfdd469c2a3500f04d3b..9e9d25c904bfda84b63cd929f7367ff465de2864 100644
--- a/assets/src/scripts/monitoring-location/components/hydrograph/time-series-graph.js
+++ b/assets/src/scripts/monitoring-location/components/hydrograph/time-series-graph.js
@@ -19,7 +19,7 @@ import {getGroundwaterLevelPoints} from './selectors/discrete-data';
 import {getFloodLevelData} from './selectors/flood-level-data';
 import {getIVDataSegments, HASH_ID} from './selectors/iv-data';
 import {getMainLayout} from './selectors/layout';
-import {getMainXScale, getMainYScale, getSecondaryYScale} from './selectors/scales';
+import {getMainXScale, getMainYScale, getYScale} from './selectors/scales';
 import {
     getTitle,
     getDescription,
@@ -236,7 +236,7 @@ export const drawTimeSeriesGraphData = function(elem, store, showTooltip) {
             segments: getIVDataSegments('secondary'),
             dataKind: () => 'secondary',
             xScale: getMainXScale('current'),
-            yScale: getSecondaryYScale('MAIN'),
+            yScale: getYScale('MAIN', 'secondary'),
             enableClip: () => true
         })))
         .call(link(store, drawDataSegments, createStructuredSelector({