(1) The Book of Purification
كتاب الطهارة
(7) Chapter: The Manners of Answering the Call of Nature
(7) باب قضاء الحاجة
Bulugh al-Maram 93 
Ahmad reported from Ibn Abbas (rad) that defecation is prohibited also at the place where water collects. [And both the two (i.e. the previous and this Hadiths) have weakness].
وَلِأَحْمَدَ; عَنِ ابْنِ عَبَّاسٍ: { أَوْ نَقْعِ مَاءٍ } وَفِيهِمَا ضَعْف ٌ 1‏ .‏


‏1 ‏- ضعيف.‏ رواه أحمد (2715)‏.‏

Reference : Bulugh al-Maram 93
In-book reference : Book 1, Hadith 111
English translation : Book 1, Hadith 99