In trading on Monday, shares of the PowerShares Global Water Portfolio ETF (PIO) entered into oversold territory, changing hands as low as $22.19 per share. We define oversold territory using the Relative Strength Index, or RSI, which is a technical analysis indicator used to measure momentum on a scale of zero to 100. A stock is considered to be oversold if the RSI reading falls below 30.In the case of PowerShares Global Water Portfolio, the RSI reading has hit 29.9 — by comparison, the RSI reading for the S&P 500 is currently 35.8. A bullish investor could look at PIO's 29.9 reading as a sign that the recent heavy selling is in the process of exhausting itself, and begin to look for entry point opportunities on the buy side. Looking at a chart of one year performance (below), PIO's low point in its 52 week range is $21.10 per share, with $25.20 as the 52 week high point — that compares with a last trade of $22.22. PowerShares Global Water Portfolio shares are currently trading off about 0.5% on the day.