Datasets produced from this study include vertical aerial photographs collected on four consecutive days during July 2001 when the river discharge was lowered in steps from approximately 350 to 150 to 120 to 90 m3/s. These were analysed at two reaches by classifying island shores directly off the imagery. The 4.2 km long reach near Priest Road has a braiding intensity typical of much of the Lower Waitaki, while the 3.6 km long reach downstream from Kurow samples the transitional, semi-braided segment of the river. At the Priest Road reach, islands were also mapped at discharges over the range 80-160 m3/s using the results of 2d hydrodynamic modelling undertaken in a previous study. The main findings were:  At the more intensely braided reach near Priest Road, the analysis of islands classified off the aerial photographs showed little difference in the frequency distribution of island size as discharge changed over the range 354-87 m3/s. As the discharge reduced from 147-116 m3/s, there was only a relatively small reduction in the number of islands with areas exceeding 0.25 ha (from 12.1 to 10.7 islands per km length of reach), while from 116 to 87 m3/s there was no change in island number. As the island size threshold is increased above 0.25 ha there were only marginal changes in the number of islands going from 147 to 116 m3/s. The total area of all islands larger than a threshold area peaked when the discharge was at 116 m3/s, irrespective of the threshold area chosen.  At the less braided reach near Kurow, the aerial photograph analysis showed fewer islands as discharge reduced from 354 to 147 m3/s, while from 147 to 87 m3/s the distributions of small-mid size islands differed erratically, with only a few less islands overall. The number of islands with areas exceeding 0.25 ha reduced from 2.8 to 1.9 per km of channel as the flow reduced from 147 to 87 m3/s. The rate of reduction in the number of islands going from 147 to 87 m3/s decreased as the island size threshold was increased above 0.25 ha. The total area of all islands larger than a threshold area increased as discharge decreased. These patterns are rendered uncertain, however, by the small number of islands observed in this reach.  The 2d hydrodynamic modelling at the Priest Road reach underestimated the number of islands and therefore the model based results were considered less reliable than those obtained from the direct mapping of island shorelines from imagery. The underestimation was because the modelling often missed sending flows through small side-braids or it drowned-out small emergent bars. These can be related to errors in the riverbed topography used by the model and to topographic smoothing associated with the modelling grid.

The National Institute of Water and Atmospheric Research Ltd (NIWA) has been commissioned by the Ministry for the Environment to estimate 11 components of the national and regional water balance of New Zealand for each of the 20 years from 1 July 1994 to 30 June 2014. This information is for use by Statistics New Zealand in a set of annual national water accounts they are developing, as part of a set of environmental accounts for New Zealand. Specifically, this work is a contribution to the Water Physical Stock Accounts. The data were analysed to summarise the water stock accounts of New Zealand and the 16 regions administered by regional councils or unitary authorities,using a combination of direct measurement and modelled data. The average annual precipitation across the country was 550,000 m3/year (equal to over nine times the volume of Lake Taupo), a reduction from previous years’ calculations. Roughly 20% of this evaporates before reaching the coast, leaving an average of 440,000 million m3/year. There is substantial variation in this water flux from year to year due to a range of climatic factors. Changes in storage – lakes, soil moisture, snow, and ice – represent very small components of the annual water balance. Use of water for hydroelectric power generation represents a significant portion of the nation’s freshwater resource, equating to 36% of the total freshwater flows, but this figure includes multiple use of water within the same catchment. Water fluxes at the regional scale vary depending on the region’s size as well as the spatial variability in the delivery and movement of water. The West Coast receives the largest portion of precipitation – 26% of the national total – and possesses 30% of the nation’s freshwater flow. Nelson City, due to its small size, accounts for the smallest portion in both cases. Canterbury accounts for the greatest portion of hydro-generation water use (mainly for the Waitaki scheme), followed by Waikato. Data are for 11 water balance components: 1. Precipitation 2. Inflows from rivers (regional scale only) 3. Evapotranspiration 4. Abstraction by hydro-generation companies 5. Discharges by hydro-generation companies 6. Outflows to sea from surface water 7. Outflows to other regions (regional scale only) 8. Net change in lakes and reservoirs 9. Net change in soil moisture 10. Net change in snow 11. Net change in ice

Datasets for work undertaken for the Christchurch City Council (CCC) include hydrometric network data (Climate variables, Rainfall, Water level and Ground water levels) from Oct-Dec 2014. Metadata include: 1 Introduction 2 Christchurch climate summary (October – December 2014) 3 Appendix: Maintenance / Fault log Data include: 1 Rainfall monitoring 2 Water-level monitoring 3 Groundwater monitoring 4 Miscellaneous data 5 Additional activities Data are derived from national climate databases and CCC rain gauges. Water-levels are derived from gauges owned by ECan, CCC and NIWA. Ground water levels are measured on either a weekly or fortnightly basis, depending on the site requirements and are measured relative to the CCC datum.

Monowai Power Station utilises the outflow from Lake Monowai. This flow is controlled by gates at the lake outlet, and travels several kilometres down the Monowai River before being diverted by a weir into a canal leading to the Power Station and released into the Waiau River. At the diversion weir, a flow is released through the fish-pass and down the Monowai River to maintain a minimum flow. The lake outflow is monitored at site no. 79712 (Monowai at Below Gates). Lake level is recorded at site no. 79713 (Lake Monowai at Hinchey’s Outlet). Flow down the lower Monowai River below the diversion weir is monitored at site no. 79715 (Lower Monowai at Below Weir); this station was installed on 10 April 2003 for resource consent monitoring. The report summarises the data from these sites for the quarterly period – 1 October to 31 December 2014, and in the context of the full record since 1977. Data and outputs cover: Daily Mean levels at Site 79713 Lake Monowai at Hinchey’s Outlet from 1 January to 31 December 2014. Daily mean outflows (m3/s) at Site 79712 Monowai River at Below Gates from 1 January to 31 December 2014. Daily mean inflows (m3/s) at Site 9540, Lake Monowai at Inflow from 1 January to 31 December 2014. Daily mean flows (l/s) at Site 79715, Lower Monowai River at Below Weir, from 1 January to 31 December 2014. Monthly mean levels (lake level in metres, in terms of Monowai datum) at Site 79713 Lake Monowai at Hinchey's Outlet from June 1977 to 31 December 2014. Monthly mean outflows (m3/s) at Site 79712 Monowai River at Below Gates from 1 October 1976 to 31 December 2014. Lake levels at Site 79713, Lake Monowai at Hinchey's Outlet from 1 October to 31 December 2014. Outflows for Site 79712 Monowai River at Below Gates (blue), and Inflows (partial range, green) for Site 9540 Lake Monowai from 1 October to 31 December 2014. Full range inflows for Site 9540, Lake Monowai from 1 October to 31 December 2014. Flow at Site 79715, Lower Monowai River at Below Weir, from 1 October to 31 December 2014. Lake Monowai at Hinchey's Outlet, lake level Lake Monowai at Hinchey's Outlet, water-level distribution from 13 May 1977 to 31 December 2014. Monowai River at Below Gates, outflow from 2 September 1976 to 31 December 2014. Lake Monowai - outflow distribution over the full period of record from 2 September 1976 to 31 December 2014.

The TopNet hydrological model was calibrated based on a combination of Virtual Climate Network stations and existing sub-daily precipitation information located within Lake Waahi surface water catchment. The hydrological models were calibrated at one continuous monitoring streamflow station in each of the surface water catchments discharging to the lakes. Due to the large potential impact of water consented activities above Awaroa at Sansons Br (within Lake Waahi surface water catchment), calibration for the Lake Waahi model was carried out taking into account only winter flows. Analysis of the calibration indicates that the models are able to better represent low flow conditions than high flow conditions when compared with streamflow observations. This result is expected due to the low density of observed precipitation gauges across the catchments and the area of the surface water catchments. Validation of the models over the whole period of record indicates that the hydrological models reproduce the range of hydrological characteristics observed at the gauging stations. Over the period 1973-2013 Lake Whangape inflows are estimated to average 5.81 cumecs (ranging from 3.80-8.8 cumecs) while Lake Waahi inflows are estimated to average 1.88 cumecs (ranging from 1.00-2.57 cumecs). Inter-comparison of the calibrated Topnet parameters used for both catchments indicates that most of the parameter multipliers are similar across both models. This indicates a consistency of the hydrological process representation across the large watershed. The TopNet hydrological model is routinely used for hydrological modelling applications in New Zealand. It is a spatially distributed, time-stepping model of water balance. It is driven by time series of precipitation and temperature data, and of additional weather elements where available. TopNet simulates water storage in the snowpack, plant canopy, rooting zone, shallow subsurface, lakes and rivers. It produces time series of modelled river flow (under natural conditions) throughout the modelled river network, as well as evaporation. TopNet has two major components, namely a basin module and a flow routing module. Climate information was obtained from Virtual Climate Station Network. Annual average precipitation and evaporation were estimated by NIWA. Spatial information in TopNet is provided by national datasets on catchment topography (i.e. 30m digital elevation model), physical (Land Cover Database, Land Resource Inventory, and hydrological properties (River Environment Classification). The method for deriving TopNet initial parameter estimates from GIS data sources in New Zealand is given in Table 1 of Calrk et al. (2008). [Clark, M.P.;Rupp,D.E.;Woods,R.A.;Zheng,X.;Ibbitt,R.P.;Slater,A.G.;Schmidt,J.;Uddstrom,M.J.(2008). Hydrological data assimilation with the ensemble Kalman filter: Use of streamflow observations to update states in a distributed hydrological model. Advances in Water Resources 31(10):1309-1324.]

The National Rivers Water Quality Network (NRWQN) has never included suspended particulate matter analyses in all 26years of its existence, although optical proxies (visual clarity; turbidity) are measured routinely. The purpose of this add-on to the NRWQN was to 'calibrate' those optical proxies to total suspended sediment (TSS) in particular rivers - to confirm the original supposition in design of the NRWQN that routine, ongoing measurement of TSS would be too expensive and not sustainable when most visits to sites intercept rivers in baseflow when TSS is relatively low and sediment flux very low. The opportunity was taken during this add-on also to measure organic content of SPM in rivers (as volatile suspended sediment; VSS) and the nutrient (N and C content) of this organic matter (particulate organic carbon, POC; particulate organic nitrogen, PON). The TSS data in the dataset has already been published (along with correlating NRWQN data) by Davies-Colley et al. (2014) and Ballantine et al. (2014). [Ballantine, D.J.; Hughes,A.O.; Davies-Colley,R.J.(2014).Mutual relationships of suspended sediment, turbidity and visual clarity in New Zealand rivers. Sediment Dynamics from the Summit to the Sea Proceedings of a symposium held in New Orleans, Louisiana, USA,11–14 December 2014)(IAHS Publ. 367, 2014). doi:10.5194/piahs-367-265-2015 Davies-Colley, R.J.; Ballantine, D.J.; Elliott, S.H.; Swales, A.; Hughes, A.O.; Gall, M.P. (2014).Light attenuation - a more effective basis for the management of fine suspended sediment than mass concentration? Water Science and Technology 69(9):1867-74. doi: 10.2166/wst.2014.096.]

This core-funded research project aimed to map river reaches that gain and lose water to, and from, the groundwater system from two regions of New Zealand (Southland and Otago). A survey of river reaches that lose and gain flow in these regions of New Zealand was conducted at Environment Southland (ES), and Otago Regional Council (ORC) with key hydrologists, groundwater scientists and ecologists to record their knowledge of the locations of flow losing and gaining reaches on rivers and streams in their region. Following these interviews, the information was then transferred to a GIS layer to enable mapping of losing and gaining reaches in Southland and Otago. This work could serve as a platform for groundwater related research or engineering by NIWA in New Zealand.

This investigation analyses historical bed-level change at seven cross-sections along the lower Rakaia River between around SH1 Bridge and the coast using data from ground surveys undertaken in 1976 and 1988/89 and from airborne LiDAR flown in 2010. It is concluded that with a few exceptions, mean bed levels along this reach appear to have been stable - at least within the level of detection and allowing for natural variation in bed levels associated with normal braided riverbed dynamics. A slight degradation trend of a few mm/yr is consistent with a response to long term coastal retreat, at least for the river within about 18 km of the coast. It is likely that much of the 0.75 m of degradation apparent over the active braidplain of the South Branch 10 km upstream from the coast between 1988 and 2010 is an artefact of errors in re-locating the section line. The investigation included: 1) Securing the historical ECan survey records and entering them into a spreadsheet. 2) Extracting the 2010 bed-levels from the LiDAR along the ECan section lines 3) Post-processing the LiDAR topography to remove remnant bias from returns off riparian vegetation. 4) Using flow-gauging data to develop a relationship between wetted cross-section area and river flow rate for use in adjusting the LiDAR mean bed-levels to include wetted bed areas 5) Plotting the overlaid sections and calculating changes in mean bed-level reporting.

Te Waikoropupu Springs emerge from a complex of aquifers (for convenience here called the Te Waikoropupu Springs aquifer complex (WaiSAC) and, because of the extremely high natural, ecological, biodiversity, spiritual, cultural and economic values associated with this remarkable feature, work towards ensuring that their values are sustained has commenced. This initiative seeks a Water Conservation Order to sustainably manage the springs themselves, plus the surface and ground waters that supply and sustain them. NIWA was requested to recommend tentative numerical water quality limits for these waters, based on a desk-top evaluation of available information on groundwater ecosystem responses to key water quality variables. Limited available information on stygofauna tolerances to a few key water quality variables (nitrates, ammonia) was reviewed and compared this toxicity information with the relevant concentrations in New Zealand’s surface water quality guidelines (i.e., the ANZECC guidelines ((ANZECC & ARMCANZ 2000)). Two key variables, organic carbon and dissolved oxygen, however are not covered by the ANZECC guidelines, but there importance to the conservation of groundwaters was reviewed. The guideline concentrations discussed here must be regarded as tentative because they are based on a review of a very small body of empirical information. A more rigorous and comprehensive approach is highly desirable, but the scant information on toxicities, tolerances and sublethal effects for groundwater ecosystems, including biofilms, and specifically for New Zealand or WaiSAC stygofauna will require significant time and other resources. (a) A literature review on stygofauna tolerances to a key water quality aquifer variables: organic carbon, dissolved oxygen, nitrate and ammonia, (b) Comparison this toxicity information with the relevant concentrations in New Zealand’s surface water quality guidelines (i.e., the ANZECC guidelines) and (c) Tentative water quality limits suggested.

A morphological model of Lake Dunstan was developed and used to better predict the future development of the sediment delta in the combined Kawarau/Dunstan Arms, to assess the change in sediment outflow quantity and composition over time and to reassess flood profiles based on future projections of the lake bed. A one-dimensional morphological model of Lake Dunstan has been constructed using the US Bureau of Reclamation’s SRH-1D modelling package. Steady-flow backwater simulations were run using 50 year and 100 year beds output from the 100 year projection simulation. These predictions are best estimates based on current knowledge but are subject to uncertainties in water inflows, sediment supply rate and gradation, and in key parameters such as channel roughness. We recommend continued monitoring of water levels and turbidity at current monitoring sites, along with regular survey of cross-sections and surface grain-size to provide ongoing data to update these predictions. In addition we recommend re-running the morphological model at 10 year intervals to update the estimates of projected flood levels. Several cross-section survey datasets have been used in this study. These datasets were all supplied by OPUS, and were sourced from the MIKE-11 model cross-section database. The representations of cross-section survey data within the SRH-1D model should therefore be identical to the survey data used in previous modelling studies using the MIKE-11 model. Using the calibrated model a 100 year projection simulation was run. Key predictions (from a February 2014 base) are: (a) The thalweg level at the Ripponvale gauging station will rise 2.6 m over 50 years and 4.7 m over 100 years with the rise occurring at a constant rate of 0.035 m/year over the 100 year period of the simulation. (b) A bed thalweg rise of 13 m at the Kawarau/Clutha confluence over the first 10 years, as the sediment tipping point passes the confluence, followed by a steady rise of 0.05 m/year over the remaining 90 years of the simulation. (c) The sediment outflow at Clyde Dam increases over time from an average of 168 kt/year over the first 20 years to 518 kt/year over the last 20 years (i.e. for year 80-100). Correspondingly, the trap efficiency for Lake Dunstan reduces from a 20 year average of 91% for year 0-20, to 72% for year 80-100. (d) The sand content of the outflow increases from 0.4% to 3.3% for years 0-20 and 80-100, respectively, and is almost completely very fine sand grade. We note, however, that it is likely that operation of the bottom sluice of the dam would lead to significantly higher outflows of sand than predicted by the model, as the model does not provide any representation of where vertically or horizontally in the cross-section the outflow occurs. Steady-flow backwater simulations were run using 50 year and 100 year beds output from the 100 year projection simulation. Key results are: (e) The flood level at Ripponvale for a 3200 m3/s flow at Clyde Dam is predicted to be RL 202.92 after 50 years and RL 204.53 after 100 years (c.f. RL 200.49 currently). (f) For the same flow at Clyde Dam, and for a headwater level at Clyde Dam at the design flood level of 195.1 m, the flood level at the Kawarau/Clutha confluence is predicted to be RL 198.95 m after 50 years and RL 200.76 m after 100 years (c.f. RL 195.34 m currently). (g) Flood levels in the Upper Clutha Arm at the Cromwell end of the lake are just 0.05 m higher than at the Kawarau/Clutha confluence for a 3200 m3/s total flow.