Integrated Watershed Management 2016/17

Integrated Watershed Management 2016/17
Balance between water availability and water needs

Problem Assume that the domestic uses of 40’000 persons are to be satisfied from a given water course with the following flow record of annual values. Is it possible ? Assuming a net capitation of 150 l/hab/day and an efficiency of 80%, the gross water requirements: Gross capitation = 150/0,8 = 187,5 l/hab/day Daily water needs = 187,5 x = 7,5 dam3 Monthly water needs = 7,5 x 30 = 225 dam3 Annual water needs = 7,5 x 365 = 2738 dam3 IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Annual flow 2,7 hm3/year IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Empirical distribution of annual flow
v(1) < v(2) < v(3) < …. < v(n) Plotting position: Weibull = i/(n+1) An empirical estimate of the probability of non-exceedance of a value of order i in a record of n values; If i is small, meaning that the value is one of the smallest in the record, i/(n+1) is close to zero. If i is large, meaning that the value is one of the largest in the8record, i/(n+1) is close to one. 1918/19, v1 1919/20, v2 1920/21, v3 1921/22, v4 1922/23, v5 1923/24, v6 1924/25, v7 1925/26, v8 1926/27, v9 1927/28, v10 1928/29, v11 …… 1984/85, vn 1, v(1) , 1/(n+1) 2, v(2), 2/(n+1) 3, v(3), 3/(n+1) 4, v(4), 4/(n+1) 5, v(5), 5/(n+1) 6, v(6), 6/(n+1) 7, v(7), 7/(n+1) 8, v(8), 8/(n+1) 9, v(9), 9/(n+1) 10, v(10), 10/(n+1) 11, v(11), 11/(n+1) ……. n, v(n), n/(n+1) 2,7 hm3/year IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Monthly flow IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Empirical distribution of annual minimum monthly flow
1918/19, Minimum monthly flow v1 1919/20, Minimum monthly flow v2 1920/21, Minimum monthly flow v3 1921/22, Minimum monthly flow v4 1922/23, Minimum monthly flow v5 1923/24, Minimum monthly flow v6 1924/25, Minimum monthly flow v7 1925/26, Minimum monthly flow v8 1926/27, Minimum monthly flow v9 1927/28, Minimum monthly flow v10 1928/29, Minimum monthly flow v11 …… 1984/85, Minimum monthly flow vn 1, v(1), 1/(n+1) 2, v(2), 2/(n+1) 3, v(3), 3/(n+1) 4, v(4), 4/(n+1) 5, v(5), 5/(n+1) 6, v(6), 6/(n+1) 7, v(7), 7/(n+1) 8, v(8), 8/(n+1) 9, v(9), 9/(n+1) 10, v(10), 10/(n+1) 11, v(11), 11/(n+1) ……. n, v(n), n/(n+1) v(1) < v(2) < v(3) < …. < v(n) Plotting position: Weibull i/(n+1) IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Empirical distribution of annual minimum monthly flow
1918/19, Minimum monthly flow v1 1919/20, Minimum monthly flow v2 1920/21, Minimum monthly flow v3 1921/22, Minimum monthly flow v4 1922/23, Minimum monthly flow v5 …… 1984/85, Esc. Mensal Mínimo vn 1, v(1), 1/(n+1) 2, v(2), 2/(n+1) 3, v(3), 3/(n+1) 4, v(4), 4/(n+1) 5, v(5), 5/(n+1) ……. n, v(n), n/(n+1) 225 dam3/month IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Average daily discharge
IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Empirical distribution of annual minimum average daily discharge
7500 m3/day = 0,1 m3/s IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Flow duration curve IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Flow duration curve 7500 m3/day = 0,1 m3/s

Look for new water sources: Superficial sources; Groundwater sources;
What can be done when the available water resources are not sufficient to satisfy water needs? Control water demand; Look for new water sources: Superficial sources; Groundwater sources; Water reuse; Dessalinization. To improve regularization capacity, when the problem is a time missmatch between water availability and water demand. IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Reservoir sizing

Water storage needs Inflow Outflow Storage Reservoirs and aquifers offer the ability to temporarily store water and to phase water availability with water demand. Albufeiras e aquíferos proporcionam uma capacidade de armazenamento temporário da água o que permite a compatibilização temporal das disponibilidade de água com as necessidades. Evaporation Reservoirs Recharge Aquifers IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Reservoir storage zones

Sizing of flood control zones
Inflow NMC Discharge Flood storage volume NPA Outflow Net volume Nme Dead storage Tempo Tempo Volume of water temporarily stored in the flood stage pool Flood peak reduction IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Sizing of the dead storage zone
Dead storage / Volume morto: Volume below the lowest uptake level / Volume abaixo do nível da tomada de água de cota mais baixa Dead storage volume depends on / Dimensão do volume morto depende de: Orography of the reservoir location / Orografia do local de implantação da barragem; Reservoir sediment inflow / Caudal sólido afluente à albufeira; Infrastruture lifetime / Expectativa de vida útil da infraestrutura. NMC NPA Sediment deposition Nme Dead storage volume Sediment inflow Bottom discharge IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Net storage pool sizing
What is the adequate size to ensure the supply of various uses with a given reliability ? Qual deve ser o valor adequado do volume útil de uma albufeira, para satisfazer um conjunto de usos com uma dada garantia de abastecimento ? Oversizing / Excesso de volume útil: Higher investment / Maior volume de investimento; Higher operating costs / Maior custo de operação; Larger environment impacts / Impactos mais significativos ; Undersizing /Défice de volume útil: Inadequate reliability /Insuficiente garantia de abastecimento; A large net storage capacity enables an increase flow regulation capacity / Quanto maior o volume maior a capacidade de regularização das afluências; Storage coeficient /Coeficiente de regularização: Creg << 1 Run-of-river reservoirs Creg < 1 - Creg > 1 Stoage reservoirs 𝑆𝑡𝑜𝑟𝑎𝑔𝑒 𝑐𝑜𝑒𝑓.= 𝑁𝑒𝑡 𝑠𝑡𝑜𝑟𝑎𝑔𝑒 𝑐𝑎𝑝𝑎𝑐𝑖𝑡𝑦 𝐴𝑣𝑔 𝑎𝑛𝑛𝑢𝑎𝑙 𝑖𝑛𝑓𝑙𝑜𝑤 IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Vt+1 = Vt + Qt – Et – R1t – R2t – St
Mass balance Evaporation Withdrawal NMC Spill Flood control NPA Inflow Net storage Energy H Nme Dead storage Volume turbinado Vt+1 = Vt + Qt – Et – R1t – R2t – St Et Vt+1 – Storage at beginning of month t+1 Vt – Storage at beginning of month t Et – Evaporation (volume) during month t Qt – Inflow during month t R1t – Volume supplied to use 1 during month t R2t – Volume supplied to use e during month t St – Spilled volume (through the spillway) during month t Qt R1t V R2t St IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Mathematical simulation
Et Area-elevation curve Curva de áreas inundadas R1t Qt Water level, H V R2t St Mass balance: Vt+1 = Vt + Qt – Et – R1t – R2t – St Estimation of evaporation: Et = At x et (volume, e.g. dam3) At - Área of the reservoir lake (e.g. km2) et – Evaporation rate (mm) A = f(V), A = f(H) Area-elevation curve V = f(H), Storage-elevation curve Inundated area, A Storage-elevation curve Curva de volumes armazenados Water level, H Stored volume, V IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Elevation-volume-area curves - Alqueva

Operating rule for a single use / Regra de operação para um único uso
Release rules Operating rule for a single use / Regra de operação para um único uso Rt = ft(Vt+Qt , Nt) Standard operating policy Política padrão Nt Vt- Storage / Volume armazenado Qt-/ Expected inflow / Volume expectável no período Nt –Water demand / Necessidade de água Kt-Storage capacity / Capacidade de armazenamento Rt-Supplied volume / Volume atribuído ao uso St-Spill / Volume descarregado IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Simulation in MS Excel IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Results IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Results K = 45’000 dam3 N = 8’000 dam3/month K = 65’000 dam3

Performance indicators
Expected benefits (€) / Benefícios expectáveis (€); Reliability / Garantia ou fiabilidade; Measures the ability to meet water demands / Mede a capacidade do sistema em satisfazer as necessidades; Time : Reliability_T = #years without supply failures/ #anos simulated years Volume: Reliability_V = Supplied volume/ Water needs Vulnerability / Vulnerabilidade: Measures the severity of supply shortages / Mede a gravidade das falhas Average duration of a supply shortage; Duração média das falhas / Supply shortage as a percentage of the demand; % das necessidades não satisfeitas em caso de falha / Robustness (Inverse of vulnerability) / Robustez (Inverso de vulnerabilidade) Resilience / Resiliência: Measures the ability of the system to recover from a supply shortage / Mede a capacidade do sistema em recuperar de uma falha; Number of months the demand is satisfied that follow a month where a suppply shortahe has ocurred over the number of supply shortages (months when demand was not satisfied). Probabilidade de não existir uma falha após uma falha (número de vezes em que uma não-falha sucede a uma falha sobre o número total de falhas) IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Yield vs storage vs reliability vs inflow variability
Yield vs Storage capacity vs Reliability / Volume fornecido vs volume da albufeira vs garantia; Yield vs Storage capacity vs Inflow variability / Volume fornecido vs volume da albufeira para diferentes variabilidades de escoamento afluente; Volume fornecido Em G3 G2 G1 > G2 > G3 G1 Reservoir capacity, K Volume da albufeira, K Yield, with a given reliability Volume fornecido com um dado valor de garantia Em S3 S2 S1 > S2 > S3 S1 Reservoir capacity, K Volume da albufeira, K IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Successive peak method
Out. 1917, Q1 Nov. 1917, Q2 Dez. 1917, Q3 Jan. 1918, Q4 Fev. 1918, Q5 Mar. 1918, Q6 …. Ago. 1990, QM-1 Set. 1990, QM Out. 1917, Q1, Q1-N Nov. 1917, Q2, Q1+Q2 – 2N Dez. 1917, Q3, Q1+Q2+Q3 – 3N Jan. 1918, Q4, Q1+Q2+Q3+Q4 – 4N Fev. 1918, Q5, …. Mar. 1918, Q6, …. …. Ago. 1990, QM-1, …. Set. 1990, QM. ….. Out. 1917, Q1. ….. Nov. 1917, Q2. ….. Dez. 1917, Q3. ….. Jan. 1918, Q4. ….. Fev. 1918, Q5. ….. Mar. 1918, Q6. ….. Ago. 1990, QM-1, . ….. Set. 1990, QM, . ….. Mass curve (Rippl diagram) S Qt - S Nt tempo Period when inflow exceeds demand Period when demand exceeds inflow IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Successive peaks method
Does not consider evaporation; Assumes demand is satisfied with a 100% reliability. S Qt - Nt K4 K3 K = Max (K1, K2, … Kn) K2 𝐾= 𝑚𝑎𝑥 𝑘 𝑚𝑎𝑥 𝑘 𝑡=1 𝑘 𝑄 𝑡 − 𝑁 𝑡 − 𝑡=1 𝑘 𝑄 𝑡 − 𝑁 𝑡 K1 time Drought period (water needs exceed water availability) Period with suficient water (water availability exceed water needs) IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Reservoir operating policies

Example Consider a reservoir with 300 hm3 of net storage capacity and with the following inflow regime, that needs to satisfy the following water needs / Considere uma albufeira com 300 hm3 de capacidade armazenamento útil e com o seguinte regime de afluências e de necessidades de água que devem ser asseguradas: Fall Winter Spring Summer Average inflow(hm3) 60 150 40 10 Coef. of variation of water needs 0,4 Water needs (hm3) 25 100 50 Assumee that the economic losses for not providing water can be estimated by a curve such as the one on the left / Considere ainda que as perdas económicas por falta de abastecimento de água podem ser estimadas por uma curva do seguinte tipo: Perdas económicas (k€) 500 Falha de abastecimento (hm3) 100 If at the end of the Winter the water stored in reservoir is 200 hm3, how much water should the reservoir supply in the spring? If at the end of the Winter the water stored in reservoir is 100 hm3, how much water should the reservoir supply in the spring? IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Problem formulation Consider the following system which supplies water for different uses / Considere a seguinte albufeira que tem um conjunto diverso de objetivos; How much water should we allocate to each use and how much water should we save for future use? / Num dado instante, qual deve ser o volume de água a atribuir a cada uso e o volume de água a armazenar para usos futuros? This question arises in two contexts: Management – how to get the maximum benefit from na existing system; exploração do máximo benefício de um sistema existente; Planning – selection of the best alternative (location and size) of a system stil to be built / seleção da melhor alternativa (definição do local e dimensão) a construir. IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Operating policies What are the factors that condition the allocation of water? Quais são os fatores que devem condicionar a decisão de distribuição dos recursos disponíveis? Available water / Volume de água disponível (i.e. armazenado); Expectations on short term inflows / Expectativas de afluências futuras (dependentes da época do ano); Water demands for each use and/or expected benefits for each use / Necessidades de água para cada uso e/ou função de benefícios expectáveis em função do volume atribuído; How to describe an operating policy? Como explicitar uma política de exploração (i.e. uma regra de operação)?: Rule curves / Curvas guia Release rules (Curvas de alocação) and balancing functions (curvas de balanço) Real-time mathematical models / Modelos matemáticos para gestão em tempo real IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Rule curves No supply restrictions Some supply restrictions
Flood control storage No supply restrictions Some supply restrictions R – Volume of water to be supplied as a function of avaliable storage and time-of-the-year. IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Operating rule for a single use / Regra de operação para um único uso
Release rules Operating rule for a single use / Regra de operação para um único uso Rt = ft(Vt+Qt , Nt) Standard operating policy Política padrão Nt Vt- Storage / Volume armazenado Qt-/ Expected inflow / Volume expectável no período Nt –Water demand / Necessidade de água Kt-Storage capacity / Capacidade de armazenamento Rt-Supplied volume / Volume atribuído ao uso St-Spill / Volume descarregado IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Hedging O conceito de “hedging” (salvaguarda; cobertura de risco
Standard operating policy Política padrão Some hedging: allows for small supply faillures to safeguard future water demands; the reliability decreases Algum “hedging”: permite antecipadamente falhas no abastecimento de menor dimensão para salvaguardar o abastecimento no futuro; o nível de garantia (número de falhas em %) é menor. More hedging: the reliability decreases further Mais “hedging”; há mais falhas que são parcialmente evitadas mas o nível de garantia (número de falhas em %) ainda menor. Maximizes the reliability: the number of faillures is smaller but when a faillure occurs no water is supplied. Maximiza o nível de garantia: há menos falhas de abastecimento mas quando há são totais. IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Single reservoir: one use
Release rule Curva A Fornece toda a água que tem, mesmo quando não é possível satisfazer a totalidade das necessidades. Curva B Só fornece quando consegue satisfazer todas as necessidades. R+S Curva A S Q N R R K V+Q V Curva B R+S S N R K V+Q IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Single reservoir: 2 uses

Q1 N V1 Q2 R1 R2 V2 Reservoir in series
Curva de alocação (release rule) R1+R2+S1+S2 Q1 N V1 Q2 R1 K1+K2 V1+V2+Q1+Q2 Curvas de distribuição (balancing functions) R2 V2 V1,V2 K2 K1 V2 V1 V1+V2 IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

We have and estimation of Q1,t + Q2,t Vt = V1,t + V2,t
How to use the release rule and the balancing functions Reservoirs in series We know V1,t and V2,t We have and estimation of Q1,t + Q2,t Vt = V1,t + V2,t Release rule: Vt + Q1,t + Q2,t -> Rt and St Vt+1 = Vt + Q1,t + Q2,t – Rt - St Vt+1 = V1,t+1 + V2,t+1 Balancing functions: Vt+1 - > V1,t+1 Vt+1 - > V2,t+1 R1,t+1 = V1,t + Q1,t – S1,t+1 – V2,t+1 R2,t+1 = V2,t + Q2,t + S1,t+1 – S2,t+1– V2,t+1 IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Reservoirs in parallel
Curva de alocação (release rule) R1+R2 Q1 Q2 N V1 V2 K1+K2 V1+V2+Q1+Q2 R1 R2 Curvas de distribuição V1,V2 V1 K1 K2 V2 V1+V2 IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

How to apply release rules and balacing curves Reservoirs in parallel
We know V1,t and V2,t Vt = V1,t + V2,t From the release rule: Vt + Q1,t + Q2,t -> Rt and St Vt+1 = Vt + Q1,t + Q2,t – Rt – St Vt+1 = V1,t+1 + V2,t+1 From the balancing functions: Vt+1 - > V1,t+1 Vt+1 - > V2,t+1 R1,t+1 = V1,t + Q1,t – S1,t – V1,t+1 R2,t+1 = V2,t + Q2,t – S2,t - V2,t+1 IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Single reservoir for energy production
Release rule R+S Q K V+Q V R When the stored volume is large, a large head is available for power production, which means that the amount of water needed to produce a given amount of energy is small; If the stored volume is small, it is not efficient to waste large amounts of water to produce a small amount of energy. E IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

One reservoir and one aquifer: one use
Depends on: Relative costs of abstraction, pumping, treatment and transport of water from both sources Evaporation rate (losses of water from superficial sources) Ratio between the reservoir capacity and the reservoir inflow (spill risk during the flooding season) Hydrogeological characteristics of the aquifer, namely its recharge, loss by seepage, storage capacity. Recarga Q V2 R2 V1 R1 N IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

And if ?? E Q1 V2 V1 Q2 Q3 R2 V4 V5 R1 Na1 R3 R4 Q4 Na2 V6 R5 Nr1
For larger and more complex systems, with a number of water sources and several users, how can we evaluate alternative management policies and select most adequate one? Q2 Q1 Q3 V2 V3 R2 V1 V4 V5 R1 Na1 R3 R4 Q4 Na2 V6 E R5 Nr1 IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Exercise A reservoir,with a net storage capacity of 2304 dam3, stores at the beginning of a given month 1560 dam3. During that specific month the inflow to the reservoir is 1780 dam3, the evaporation is 100 dam3. If 600 000 m3 are supplied what is the discharge through the spillway. IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

Exercise Consider a reservoir, with a net storage capacity of m3. At the beginning of a 4-month period the net storage at the reservoir is 900 dam3 and the expected monthly inflows are 3000 dam3, 1600 dam3, 1280 dam3 and 999 dam3, after evaporation is deducted. If the monthly water supply target is 1900 dam3, what is final net storage at the reservoir and what is water supply deficit, if any? How much is discharged through the spillway? IST: Integrated watershed management © Rodrigo Proença de Oliveira, 2016

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