Lakeside North Mound Wang Wei A riot of trees contrast with crimson railings, At northern end: the mound of Lakeside North. While in and out of green woods, winking, trailing, The South Stream wends around its snakelike course. 王维 北垞 北垞湖水北，杂树映朱阑。 逶迤南川水，明灭青林端。
Wang Wei appears to be just at play in this poem. I think he likes the way the words “water” and “north” rhyme in Chinese - they each appear twice, making up 20% of this short poem. He throws in “south,” and a word for river that rhymes with south, as well. (These rhymes don’t work in English, so I tried to represent the emphasis on soundplay with the heavy echoes in lines two and four.) In the remaining 14 characters of the poem, he still manages to construct a lovely paired image of a red railing against green trees, and a shining rivulet running through shady woods: a visual rhyme to equal his joyful sound rhymes. He makes no explicit mention of any emotional state, but this is one of the happiest poems I know.
Ignore the paragraph above, I was being silly! (see helpful comment from Charles below)
Pei Di's poem at the same site (prose translation):
The South Hill lies below Northern Mound/ we stand in the boathouse and look at Lake Qi./ Every time we want to collect firewood/ our boat sets out through pondweed and sweet flag.
Lovely play with words
Good grief, no, Wang Wei does not like how the words “water” and “north” rhyme. They do not rhyme because Wang Wei did not speak modern Mandarin. 水 is in the rhyme category 上聲四紙, while 北 had three pronunciations during the Tang and is found in the rhyme categories 去聲十一隊，入聲八黠，and 入聲十三職. You also say that he includes a word for river that rhymes with south. This is also incorrect. 南 is in the rhyme category 下平聲十三覃, and 川 is in the rhyme category 下平聲一先. This poem is therefore not happy or playful in the manner you suggest.