4. Water Resources and Water Related
Disasters in New Zealand :the Role of Agro-environmental Education
Noel A. TRUSTRUM1 and N. J. PRESTON

Quantifying New Zealand’s water
resource
On a world scale New Zealand has plenty offresh water, but it does experience severe climaticand hydrological extremes. New Zealand has amaritime climate, with the prevailing westerly
winds delivering moisture-laden air from theSouthern Ocean and Tasman Sea. The mountainous spine of the country is oriented perpendicular
to this airflow, resulting in substantial orographic
rainfall, especially on the western parts of boththe North and South Islands (Fig. 1). In addition,
tropical and sub-tropical cyclones frequently
track south toward New Zealand in the summer
and autumn months. High rainfall, steep topography and a high density of rivers generate highrunoff.
There is a substantial rainfall gradient withhigh rainfall in the west (up to 10 m) and rainshadow zones in the east (as low as 400 mm/a).
In addition to this spatial variability, there is alsoa degree of temporal variability in rainfall receipt.
Seasonality is not as strongly marked in New
Zealand’s rainfall regime compared with mostother Pacific Rim countries, with most areas
receiving reasonably well-distributed rainfall
throughout the year. However, New Zealand does
experience inter-annual and decadal variability in~ Southernrainfall as a result of the El Nin
Oscillation. As Fig. 2 illustrates, this is pronounced in the drier eastern regions. Because
they have lower annual rainfalls anyway, substantial negative deviations from average can mean
drought. On decadal timescales these droughts

1

Fig. 1 Average annual rainfall (mm)(Source : Tomlinson 1992).

can be punctuated by periods of storminess (Page& Trustrum 2000). As with rainfall, the runoff
regime is variable, with frequent flood events
alternating with periods of low flow, as indicatedby the coefficients of variability given in Fig. 3.

A century of anthropogenic disruption
to the hydrological regime
In the mid to late 19th C, European settlement
led to extensive deforestation and conversion to
pasture over large areas of New Zealand. Muchof this conversion took place on steepland litholo-

Landcare Research NZ Ltd., Private Bag 11052,
Palmerston North, New Zealand43

gies naturally predisposed to erosion.
Deforestation, in combination with naturally highand frequent rainfall, initiated a particularly
intense phase of anthropogenic erosion that destabilised the landscape and led to extensive aggradation of river systems in response to theincreased sediment inputs (Page & Trustrum1999). These dramatic landscape transformations
and associated erosion have progressively
reduced topsoil regolith depths. The effect of thisis decreased soil water storage capacity on hillslopes, which makes soils more susceptible toeither saturation or desiccation than their forest
antecedents. Runoff is therefore more likely to bedelivered as overland flow than as through flow
(Trustrum & De Rose 1988). A consequence of
this is a long term change in the runoff regime,with a greater frequency of extreme high and low
flows.

Fig. 2 Variability of average annual rainfall(Source : NZ Meteorological Service
1985, after Mosley & Pearson 1997).

Fig. 3 Mean flows (m3/s) and coefficients of variation ofmajor New Zealand rivers (from Duncan 1992).

44

issues, even for a country with a population of
only ~4 million with nearly the same land area
(270,000 km2) as Japan (population 125 million).
Water contributes directly to New Zealand’s economic performance. The economic value of
ecosystem services provided by New Zealandrivers and lakes (including hydroelectric generation, irrigation, waste processing and water supply) is estimated to be $US2002 4,300 million perannum representing ~11% of New Zealand’s
GDP (Patterson & Cole 1999).
In New Zealand, where 70% of the population is concentrated on the floodplains and lower
reaches of rivers (Fig. 4), there is a high demandon the water resource for irrigation, domestic
consumption and waste water treatment. This
demand often exceeds the available resource. For
example, although the use of water for processing
waste represents only 8% of the ecosystem service value, critical limits to the ability of rivers to

Cultural and economic values of waterin New Zealand
Maori people, many of whom live in thesehighly degraded steepland areas, draw a close
connection between the wellbeing of the people
and the environmental state of the land and rivers(Harmsworth et al. 2002). This connectivity isembraced in the following quote from a Maoriwoman : “the river is our taonga (treasure) andour life essence. Land erosion reflects how weare becoming as a people. We are losing ourmana (prestige/authority/honour). The river iseating away at the land. Without this land we arenothing”. This quote illustrates that in the New
Zealand context cultural and ethical considerations are fundamental to the way in which thewater resource is managed.
The variable distribution of New Zealand’s
abundant water resource raises water allocation

Fig. 4 Location of main population centres of New Zealandsituated on floodplains (Source: Report of the Royal
Commission to Inquiry, New Zealand, 1949. Govt.
Printer, Wellington)45

absorb waste are often reached (Patterson & Cole1999). The resulting pollution and degradedwater quality represent a long-term problem forecosystem recovery because mitigation and rehabilitation programmes must take into consideration social and economic factors such as property
rights.

Erosion and sedimentation
Extreme rainfall induces not only floods, but
extensive episodes of erosion as well. As Fig. 5
indicates, rainfall-initiated land sliding is common throughout much of New Zealand. This
form of erosion has been extensive in the past but
may decrease in significance as the landscaperelaxes from the major deforestation episode (seeCrozier & Preston 1999). Nevertheless, New
Zealand rivers carry high volumes of sediments
generated as a result of erosion (Fig. 6), discharging over 1% of global sediment yield from acountry that occupies only ~0.2% of the world’s
landmass. This illustrates clearly the high incidence of rainfall-related erosion, and disasters
such as overbank deposition and associated damage to infrastructure are not uncommon. Higherosion-related sediment yields are driven by bothnatural processes (e.g., Cropp River in Westland,
Fig. 6) and those heavily influenced by anthropogenic alteration of the landscape (e.g., Waipaoa
and Waiapu Rivers on the East Cape of the North
Island, Fig. 6). The extent to which sediment disasters are linked to the multiple interests of communities and industry can only be understood atcatchment scales. It is at this scale that magnitude-frequency relationships established between
hillslope erosion process and downstream sediment yield can provide the template for targeted
mitigation strategies (Trustrum et al. 1999).
Sediment disasters impact directly (and indirectly) on the economy. It has been estimated thatthe total annual cost of damages is $US2002 52 million, with a further $US2002 12 million spent on
mitigation of soil erosion and delivery of sediments to streams (Krausse et al. 2001). There arealso downstream implications in terms of water
quality. In fact, water quality is a topical issue in
New Zealand, with implications for human consumption, recreation, in-stream biota, commercial
and recreational fisheries, and hydroelectric generation.

Floods and Droughts
Ironically, this variability of water supply
also represents a hazard and a cost to New
Zealand in the form of water-related diasters suchas floods and droughts. Almost all New
Zealand’s population centres are situated onfloodplains (Fig. 4), and have been subject tosome degree of flooding at various times.
Annually flood damage costs about $US2002 55
million (Krausse et al. 2001), and this has led toconsiderable expenditure on flood protection,with about $US 2002 1.06 billion spent over theperiod 1951/84 on remediation and mitigation(Waugh et al. 1997).
The significance of droughts in New
Zealand is less well documented, at least in part
because drought tends to be regional rather thanlocalised in its impact. It is difficult to quantify
the frequency of drought, although the distribution of rainfall variability given in Fig. 2 can beused as a broad indication of susceptibility. It
does seem that somewhere in New Zealand will
experience drought every 2 or 3 years (Waugh et
al. 1997). Equally, it is difficult to quantify thecosts associated with drought although farmers
have traditionally been only too aware of theireconomic importance. For example, the 1988/89
drought on the eastern South Island cost farmers
some $US2002 227 million in lost production thatwould have included direct stock losses and lost
primary productivity (Waugh et al. 1997). A
major cost is reduced hydroelectric generation
capacity. This is especially significant for thelarge South Island hydroelectric schemes where a“power crisis” in 1991/92 and more recent watersupply deficits have highlighted the vulnerabilityof New Zealand’s hydroelectric capability when“dry winters” are not fully incorporated into forecasts of water utilisation.

Sustainability of the water resource
Given the huge difference between the highvalue of the water resource to the New Zealandeconomy and the small amount of money spent
on remediation and disaster mitigation, it is perti-

46

Fig. 5 Recorded incidents of landslide
generating rainfall, 1870-1955(Source: Glade 1998).

Fig. 6 Suspended sediment yields and mean annual
rainfall isohyets. Sediment yield is proportional
to bar size (Source : Hicks et al. 1996).

nent to ask whether enough is being done to protect the intrinsic water resource. To address thisquestion it will be necessary to identify the costof depletion of the resource in terms of the loss ofsoil water storage capacity, degraded water quality, and greater variability in the flow regime.
With ever increasing demands on water resources- e.g., global consumption of fresh water is doubling every 20 years (Vidal 2002) - strategies tosustain the resource will need to be rapidly implemented.

cycle, although it appears that study of the cycle
itself is not addressed (Ministry of Education
1993). Natural hazards are included, but teaching
will generally focus on more spectacular phenomena such as volcanoes and earthquakes. For thisreason, awareness of flooding is probably greaterthan that of drought.
In Geography natural hazards are specifically addressed in Year 11, the concept of sustainability is introduced by Year 12, and in Year
13 the interaction between human and biophysical systems is addressed along with the topic ofresource management legislation (Ministry of
Education 1990). At a national level, annually
35-40% of students will study Geography to Year13, and might reasonably be expected to havesome awareness of issues of hazards and/or sustainability of resource use. However, applicationof these concepts specifically to water is not prescribed; it is very much at the discretion of individual schools. It is unlikely, therefore, that secondary education contributes significantly toawareness of flood/drought issues among the general population.
At university level aspects of water resource

How is agro-environmental education
addressing these issues?
At a secondary education level, issues ofhydrology and water resource use are potentiallyaddressed within three subject areas: Geography,
and, to a lesser extent, Science and Social Studies(J. Lynex, pers. comm.). However, Geography is
not a compulsory subject, while Social Studies
and Science are compulsory only for the first 2
years of secondary education (i.e. until Year 10).
Within the Science curriculum, students may
focus on various components of the hydrological47

Table 1. Numbers of tertiary-level students enrolled within broad subject areas as of July 2000.
(Source : Prof. P.J.J. Kamp, New Zealand-France Cooperative Workshop, July 2002).
Field of Study

Number

Percentage

Business
Humanities
Education
Natural and Applied Sciences
Medicine & HealthSocial Sciences
Engineering
Art & Music
Computing
Agriculture, Horticulture, Forestry, Fishery
Law
Sport & Recreation
Architecture & Town Planning
Mathematics
Other

55,452
26,72525,26817,73416,092
12,634
9,827
9,835
9,300
7,300
6,205
5,171
3,867
150
51,838

21.54
10.38
9.82
6.89
6.25
4.91
3.82
3.82
3.61
2.84
2.41
2.01
1.50
0.06
20.14

Totals257,398

100.00use and natural hazard assessment are addressedby various departments (Geography, Geology,
Earth Sciences, Environmental Studies, etc.),
making it difficult to quantify the students
involved. Professor Peter Kamp (University ofWaikato) has compiled figures for the number ofstudents enrolled within different courses of study
at all tertiary institutions (Table 1). While issuesof resource use and hazard mitigation can arise inother subject areas, the most relevant category is
Natural and Applied Sciences. Less than 7% of
all tertiary students are enrolled in courses in thiscategory, and not all of these will actually consider the water resource.
Table 1. Numbers of tertiary-level students
enrolled within broad subject areas as of July
2000. (Source : Prof. P.J.J. Kamp, New ZealandFrance Cooperative Workshop, July 2002).
Notwithstanding a relatively low level ofattention given to these issues within formal education, the general awareness of water issues
within the New Zealand community is highbecause of the dependence on water and the frequency of hydrological disasters. At community
level, a wide range of efforts is being made to
improve both awareness and understanding. The
Ministry of Civil Defence has produced an awareness and practical advice leaflet for floods.
Legislation relating to flood protection has been
in existence since the 1940s, and comprehensive
resource management legislation was enacted in1991. Management of New Zealand’s environmental resource is based on river catchments as
the fundamental unit of organisation, and theregional and district councils responsible for thismanagement use a range of approaches including
community participation groups, education andawareness campaigns, a range of financial incentives and subsidies, and regulation. In addition,
there are a number of non-governmental organisations and trusts that facilitate community participation in restoration programmes.
Extensive work has been done in the last
half century both in quantifying the resource andits variability, and in designing protection works.
More recently, attention is moving towards amore integrated understanding of catchment
dynamics and their behaviour through time. New
research programmes integrate land and water
environments to assess land-use effects on sediment and carbon fluxes from river basins tooceans, and the potential role they play inaddressing global greenhouse gas and climatechange issues (Trustrum et al. 2002).

Summary
Although water resources (and related disasters) are fundamental to New Zealand’s social andeconomic wellbeing, questions can be raised withregard to their sustainability given the potential
for depletion over the longer term. Furthermore,48

the degree to which formal education focuses onthese issues is minimal with few tertiary students
studying environmental processes and theirimpacts. Although general public awareness is
fickle and only becomes heightened following
extreme storms and droughts, management ofwater resources and their impacts is embodied inresource management law and is implemented bynational and regional organisations with increasing levels of community participation.

Zealand Curriculum. Learning Media Ltd,
Wellington.
Mosley, M.P. & Pearson, C.P. 1997. Introduction: hydrological extremes and climate in New
Zealand. In Mosley, M.P. & Pearson, C.P.
(eds.) Floods and Droughts : the New
Zealand Experience. New ZealandHydrological Society, Wellington. 1-14.
New Zealand Meteorological Service 1985.
Climatic Map Series, Part 6, Annual
Rainfall. Misc. Publ. 175, New ZealandMeteorological Service, Wellington.
Page, M.J. & Trustrum, N.A. 1999. Landscapetransformation since 1900. In Thorn, B. (ed.)
Geographica : The Complete Illustrated
Reference to New Zealand and the World.
David Bateman, Auckland. pp. 82-83.
Page, M.J. & Trustrum, N.A. 2000. High resolution lake sediments from New Zealand - arecord of late Holocene storm history, vegetation change and landscape response.
PAGES Newsletter 8 (3), 17-18.
Patterson, M. & Cole, A. 1999. Assessing thevalue of New Zealand’s Biodiversity. Schoolof Resource and Environmental Planning,
Massey University. 88 pp.
Tomlinson, A.L. 1992. Precipitation and theatmosphere. In Mosley, M.P. (eds.) Watersof New Zealand. New Zealand HydrologicalSociety, Wellington. 63-74.
Trustrum, N.A. & De Rose, R.C. 1988. Soil
depth-age relationship of landslides on
deforested hillslopes, Taranaki, New
Zealand. Geomorphology 1, 143-160.
Trustrum, N.A., Gomez, B., Page, M.J., Reid,
L.M. & Hicks, D.M. 1999. Sediment production, storage and output : the relative roleof large magnitude events in steepland catchments. Zeitschrift für Geomorphologie
Suppl. 115, 71-86.
Trustrum, N.A., Tate, K.R., Page, M.J.,
Sidorchuk, A. & Baisden, W.T. 2002.
Towards a national assessment of erosionrelated soil carbon losses in New Zealand. In
Yuren, J. (ed.) Sustainable Utilization of
Global Soil and Water Resources.
Proceedings of the 12th ISCO Conference,
Beijing. Vol. 3. 182-186.
Vidal, J. 2002. Blue gold : Earth’s liquid asset.
Earth (The Guardian), August. 6-8.

References
Crozier, M.J. & Preston, N.J. 1999. Modellingchanges in terrain resistance as a componentof landform evolution in unstable hill country. In Hergarten, S. & Neugebauer, H.J.
(eds.) Process Modelling and Landform
Evolution. Lecture Notes in Earth Sciences.
Springer, Heidelberg. 267-284.
Duncan, M.J. 1992. Flow regimes of New
Zealand rivers. In Mosley, M.P. (ed.) Watersof New Zealand. New Zealand HydrologicalSociety, Wellington. 13-27.
Glade, T. 1998. Establishing the frequency andmagnitude of landslide-triggering rainstorm
events in New Zealand. Environmental
Geology 35 (2-3), 160-174.
Harmsworth, G., Barclay-Kerr, K. & Reedy, T.
2002. Maori sustainable development in the
21st century : the importance of Maori values, strategic planning and information systems. Journal of Maori and Pacific
Development 3(2), 40-69.
Hicks, D.M., Hill, J. & Shankar, U. 1996.
Variation of suspended sediment yields
around New Zealand : the relative importance of rainfall and geology. In Walling,
D.E. & Webb, B.W. (eds.) Erosion and
Sediment Yield : Global and Regional
Perspectives. IAHS Publ. No. 236. 149-156.
Krausse, M., Eastwood, C. & Alexander, R.R.
2001. Muddied Waters : Estimating the
National Economic Cost of Soil Erosion and
Sedimentation in New Zealand. Landcare
Research NZ Ltd, Lincoln. 47 pp.
Ministry of Education 1990. Syllabus for
Schools. Geography Forms 5-7. Learning
Media Ltd, Wellington.
Ministry of Education 1993. Science in the New

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Waugh, J., Freestone, H. & Lew, D. 1997.
Historic floods and droughts in New
Zealand. In Mosley, M.P. & Pearson, C.P.
(eds.) Floods and Droughts : the New
Zealand Experience.
New ZealandHydrological Society, Wellington. 29-50.

method of stabilizing hill slopes erosion although
not necessarily the best for biodiversity or tomaintain traditional farming infrastructures. On
pasture slopes space planting of gullies and hillslopes by willows and poplar trees has been astandard countermeasure with varying degrees ofsuccess.
Question : Reducing the water holding capacityof the soil, is there any relation with the deforestation technique? Because if you use machinery, the soil becomes compact and the infiltration
capacity becomes less considering, not only sealing and crushing.
Answer : Yes studies (Phillips et al) have shownthat machinery does compact soils (on slopes
below 25o where machines are used) and hencecause more sheet and rill erosion but does notaffect land sliding significantly. Soil compaction
certainly reduces water-holding capacity.
Question : For the time being the NZ has noproblem regarding the water resources (ex. NZ
has a large amount of freshwater). What will be
your country’s anticipation related to global climate change?
Answer : The temporal or spatial distribution of
rainfall does cause problems of water allocation
especially in the dryer east coast “rain shadow”
regions. A change in global climate change ispredicted to cause more extremes of floods, sediment disasters and droughts.
Question : What specific human activities are
involved in anthropogenic erosion?
Answer : Includes all human activities that might
affect erosion rates.
Question : What is the estimated range of anthropogenic erosion in New Zealand in tons/ha/yr?
Answer : Large range but in general anthropogenic erosion rates are on order of magnitude
greater for landscapes converted from forest to
pasture. In the highly erosion prone east coast
tertiary soft rock geologies average sedimentyields for the river basin are 6,750 tons/km2/yr-1
which is high by global standards.
Question : What kind of soil and rock on themountainous area can cause serious erosion inyour country?
Answer : Steep mountainous areas are comprisedof “older” pre-cretaceous rocks (including
greywache’s and granites etc.). The “softer”
younger rocks, which flank both the eastern and

NEW ZEALAND : DISCUSSION
Question : Can you clarify further on the concept
and meaning of changing of water holding capacity during a century of NZ anthropogenic disruptions?
Answer : As the mean hill slope soil depth isreduced as a result of the expansion of landslide
scans that progressively strip the soil mantles tobedrock the effect is to decrease soil water holding capacities on hill slopes, which makes soils
more susceptible to either saturation than theirforest antecedents. Run- off is therefore more
likely to be delivered as overland flow than as
through flow. A consequence of this is a longterm change in the run-off regime, with greater
frequency of extreme high and low flows.
Question : Is the breakdown of hill slopes into <28o ; 28-42o ; >42o common or is standard use in
NZ? Do you use it also?
Answer : The breakdown of hill slopes to <28o,
20 -32, 32-42 and >42o is based on a significant
number of hill slope measurements. For example,
little landslide erosion occurs below 28o from 2832o there is significant land sliding especially onhill slopes converted from forest to pasture. Little
erosion occurs on this slope groups under forest.
Above 32o erosion can be more significant under
forest (natural erosion) and it is on these same hillslopes that rapid adjustment of hill slope soil
depths occur after deforestation and conversion to
pasture.
Question : Could you mention about the main
disaster among the water related disasters in moredetails including the countermeasures being
adopted in New Zealand?
Answer : More details are provided in my paper
pages 6,7 & 8. I agree that countermeasures have
only been covered in a generic form but NZ does
have an extensive network of flood control
schemes on all populated floodplains. On hillslopes block planting of whole tributary catchments by radiata pine is the most effective

50

western sides of the axial ranges, are comprisedof tertiary sandstones, siltstones and mudstones
that have all been rapidly uplifted from theirrespective sedimentary basins. These “soft”
rocks are very susceptible to erosion.

51