# River-Wide Habitat Availability for Fish Habitat Guilds: Implications for In-Stream Flow Protection
## 3 Results
The river discharge guidelines developed from the habitat time-series analysis describe the variable discharge conditions characteristic of the Niobrara River depending on the bioperiod (Table 4). Base HST discharge values ranged from 0.14 cfsm to 0.19 cfsm among bioperiods in segments 1 and 2. During the critical period of rearing and growth the base HST discharge threshold was 0.14 cfsm and discharges below this threshold for longer than 92 days may have significant influence on biota (defined as a catastrophic condition, Table 4). Additionally, subsistence HST discharge during the rearing and growth period occurred at 0.05 cfsm and discharges below this threshold for longer than eight days may have a significant influence on biota. Base HST discharge values ranged from 0.09 cfsm to 0.13 cfsm among bioperiods in segment 3. Subsistence HST discharge events ranged from 0.06 cfsm to 0.07 cfsm in segment 3 and may be sustained for durations of five to 21 days depending on the bioperiod. Figure 3: The percent of channel area available to each fish guild across a range of discharges for each river segment of the Niobrara River. The bolded red line is the percentage of the channel area that was considered wetted area. Note different scales used on river discharge axis. Discharge levels are quantified as ft3 s-1 mi-1 (cfsm). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Segment**} & \multirow{2}{*}{**Discharge Condition**} & \multicolumn{5}{c}{**Biopperiod**} \\ \cline{3-7}  & **RG** & **OE** & **OL** & **ES** & **LS** \\ \hline \multirow{6}{*}{1 and 2} & Base (Common) discharge (cfsm) & 0.14 & 0.16 & 0.17 & 0.19 & 0.19 \\  & _Duration under persistent (days)_ & 32 & 45 & 21 & 18 & 20 \\  & _Catastrophic duration (days)_ & 92 & 92 & 59 & 55 & 47 \\  & Trigger Discharge (cfsm) & 0.06 & 0.10 & 0.08 & 0.12 & 0.10 \\  & _Duration under persistent (days)_ & 8 & 9 & 7 & 7 & 7 \\  & _Catastrophic duration (days)_ & 16 & 18 & 8 & 11 & 11 \\  & Subsistence (Rare) Discharge (cfsm) & 0.05 & 0.08 & 0.06 & 0.11 & 0.09 \\  & _Duration under persistent (days)_ & 5 & 6 & 4 & 3 & 6 \\  & _Catastrophic duration (days)_ & 8 & 10 & 5 & 8 & 9 \\  & Base (Common) Discharge (cfsm) & 0.09 & 0.12 & 0.13 & 0.10 & 0.10 \\  & _Duration under persistent (days)_ & 47 & 46 & 22 & 39 & 12 \\  & _Catastrophic duration (days)_ & 92 & 92 & 59 & 54 & 29 \\  & Trigger Discharge (cfsm) & 0.06 & 0.07 & 0.08 & 0.07 & 0.07 \\
3 & _Duration under persistent (days)_ & 11 & 8 & 7 & 6 & 4 \\  & _Catastrophic duration (days)_ & 30 & 25 & 12 & 9 & 6 \\ Subsistence (Rare) Discharge (cfsm) & 0.06 & 0.06 & 0.07 & 0.07 & 0.07 \\  & _Duration under persistent (days)_ & 10 & 4 & 4 & 3 & 3 \\  & _Catastrophic duration (days)_ & 21 & 6 & 7 & 6 & 5 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Discharge levels (cfsm) recommended for each bioperiod in all three river segments of the Niobrara River, NE. Bioperiods are based on seasonal changes in precipitation and temperature as well as on life-history stages of fishes and include: Rearing and growth (RG; 1 July to 30 September), overwinter early (OE; 1 October to 31 December), overwinter late (OL; 1 January to 28 February), early spring (ES; 1 March to 14 May), and late spring (LS; 15 May to 30 June). Recommended discharges based on a time series of long-term hydrologic data from the Niobrara River and continuous under threshold (UCUT) analysis [26]. A persistent event is likely to occur every few years, but at the intra-annual scale, these long events are unusual (i.e., do not happen more than twice in a year). Catastrophic events are assumed to occur on a decadal-scale. Discharge levels are quantified as ft3 s-1 mi-1 (cfsm).