PROBLEM TO BE SOLVED: To provide a water reservoir sheet and laying structure of Water reservoir sheet, where the sheet can be laid on the inner wall surface of a water reservoir tank in a state of being tightly contacted with each other, and folded into a substantially flat state when not in use.SOLUTION: According to the present invention, a water reservoir sheet 10A comprises: a bottom sheet 101 formed in a substantially rectangular shape in a width plan view； a long side sheet 102 contiguous with both long edge portions of the bottom sheet 101； a short side sheet 103 continuously formed on the ends of short edge portions of the bottom sheet 101； and an exit corner sheet 104 continuously provided between the end of the long side sheet 102 and the end of the short side sheet 103. An exit corner portion 105 where the long side sheet 102 and the short side sheet 103 intersect with each other is formed to have a size and shape to cover an incoming corner portion 204 where a long side wall portion 202 and a short side wall portion 203 of the water reservoir tank 20 intersect with each other. On both end portions of the long side sheet 102, folding ruled lines 120, which are foldable in two in a substantially triangular shape, are attached.SELECTED DRAWING: Figure 8【課題】この発明は、貯水槽の内壁面に対してぴったりと密着させた状態に敷設することができるとともに、不要時において略平坦な状態に折り畳むことができる貯水槽用シート及び貯水槽用シートの敷設構造の提供を目的とする。【解決手段】貯水槽用シート１０Ａを、幅平面視略矩形に形成した底部シート１０１と、底部シート１０１の長辺側両縁部に連設した長辺部シート１０２と、底部シート１０１の短辺側両縁部に連設した短辺部シート１０３と、長辺部シート１０２及び短辺部シート１０３の端部間に連設した出隅部シート１０４で構成している。長辺部シート１０２と短辺部シート１０３とが交わる出隅部１０５を、貯水槽２０の長辺側壁部２０２と短辺側壁部２０３とが交わる入隅部２０４を覆う大きさ及び形状に形成している。長辺部シート１０２の両端部に、略三角形に二つ折り可能な折り曲げ罫線１２０を付設している。【選択図】図８
