diff --git a/src/app/components/pb-schema/pb-schema.component.ts b/src/app/components/pb-schema/pb-schema.component.ts
index 40217b619a7b18f79624bd14496f2433fe7ca2a1..e1e74c9e6fcf715c1a11c1da7dbf121960ea5801 100644
--- a/src/app/components/pb-schema/pb-schema.component.ts
+++ b/src/app/components/pb-schema/pb-schema.component.ts
@@ -5,7 +5,7 @@ import * as screenfull from "screenfull";
 import { Screenfull } from "screenfull"; // @see https://github.com/sindresorhus/screenfull.js/issues/126#issuecomment-488796645
 
 import {
-    PreBarrage, PbBassin, PbBassinParams, PbCloison, Observer, IObservable
+    PreBarrage, PbBassin, PbBassinParams, PbCloison, Observer, IObservable, ParamDefinition, ParamValueMode
  } from "jalhyd";
 
 import * as mermaid from "mermaid";
@@ -20,6 +20,7 @@ import { FormulairePrebarrage } from "../../formulaire/definition/form-prebarrag
 import { AppComponent } from "../../app.component";
 
 import { fv } from "app/util";
+import { FormulaireNode } from "app/formulaire/elements/formulaire-node";
 
 /**
  * The interactive schema for calculator type "PreBarrage" (component)
@@ -491,10 +492,35 @@ export class PbSchemaComponent implements AfterViewInit, AfterContentInit, OnIni
         return this.i18nService.localizeText("INFO_FIELDSET_COPY");
     }
 
+    /**
+     * Set value of all single parameters to undefined, except for the given parameter ids
+     */
+    private emptyFields(basin: PbBassin, except: string[] = FormulaireNode.NeverEmptyFields) {
+        // save current calculated param, as setting value on a CALC param will
+        // change its mode and choose another calculated param by default
+        let calcP: ParamDefinition;
+        for (const p of basin.parameterIterator) {
+            if (
+                [ParamValueMode.SINGLE, ParamValueMode.CALCUL].includes(p.valueMode)
+                && !except.includes(p.symbol)
+            ) {
+                if (p.valueMode === ParamValueMode.CALCUL) {
+                    calcP = p;
+                }
+                p.setValue(undefined);
+            }
+        }
+        // restore original calculated param
+        if (calcP !== undefined) {
+            calcP.setCalculated();
+        }
+    }
+
     /** Adds a new lone basin */
     public onAddBasinClick() {
         const newBasin = new PbBassin(new PbBassinParams(20, 99));
         this.model.addChild(newBasin);
+        this.emptyFields(newBasin);
         this.clearResults();
         this.refreshWithSelection(newBasin.uid);
         this.calculatorComponent.showPBInputData = true;
diff --git a/src/app/formulaire/elements/formulaire-node.ts b/src/app/formulaire/elements/formulaire-node.ts
index b0e214f5ebd3f41a30c9918b2aea7ae5b4b3056c..4d48607af879a7bbfe7aadd459e61737db0787b6 100644
--- a/src/app/formulaire/elements/formulaire-node.ts
+++ b/src/app/formulaire/elements/formulaire-node.ts
@@ -12,7 +12,7 @@ export abstract class FormulaireNode implements IObservable {
     /**
      * fields in fieldset that must not be empty due to enableEmptyFieldsOnFormInit option
      */
-    protected static NeverEmptyFields = ["Cd0", "CdWS", "CdGR", "CdGRS", "CdCunge", "CdWR", "CdO", "CdT", "CdWSL"];
+    public static readonly NeverEmptyFields = ["Cd0", "CdWS", "CdGR", "CdGRS", "CdCunge", "CdWR", "CdO", "CdT", "CdWSL"];
 
     /** aide en ligne */
     protected _helpLink: string;